feat(backend): push notifications module (FCM HTTP v1)

New global push/ module mirroring mail/ and files/storage/:
- PushProvider abstraction; default LogPushProvider (no delivery, logs),
  PUSH_PROVIDER=fcm switches to FcmPushProvider — Firebase Cloud Messaging
  HTTP v1, authenticated by a service-account JWT exchanged for an OAuth
  token (no extra dependency; jsonwebtoken does the signing). Prunes tokens
  FCM reports as invalid.
- DeviceToken model (token + platform, bound to a User or GuestAccount),
  migration + added to the sync log.
- POST /api/push/register + /unregister (any of the three token kinds).
- PushService.notifyChannel() resolves a channel's readable audience
  (DIREKT participants / LT / Gemeinde members + guests / whole KC for
  broadcast), looks up their device tokens (minus the sender), sends.
- ChatService.sendMessage() fires it best-effort after persisting.

New env: PUSH_PROVIDER, FCM_PROJECT_ID (default konfi-castle-app),
GOOGLE_APPLICATION_CREDENTIALS.

Verified against local Postgres: register a token, send a Gemeinde-group
chat message from another member -> log-push logs "would push ... to 1
device". Real FCM send needs the service-account JSON. npm test 56.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

backend/.env.example

@@ -31,6 +31,14 @@ SMTP_SECURE="false"
 SMTP_USER=""
 SMTP_PASS=""
 
+# Push: defaults to "log" (no delivery). Set PUSH_PROVIDER=fcm plus
+# FCM_PROJECT_ID and GOOGLE_APPLICATION_CREDENTIALS (path to a Firebase
+# service-account JSON with the "Firebase Cloud Messaging API" enabled) to
+# send real notifications via FCM HTTP v1.
+PUSH_PROVIDER="log"
+FCM_PROJECT_ID="konfi-castle-app"
+GOOGLE_APPLICATION_CREDENTIALS="/absolute/path/to/serviceAccount.json"
+
 # File storage: defaults to Nextcloud via WebDAV; set STORAGE_PROVIDER=s3 to
 # use an S3-compatible bucket instead (see S3_* vars below).
 STORAGE_PROVIDER="webdav"

backend/prisma/migrations/20260910093835_device_tokens/migration.sql

@@ -0,0 +1,21 @@
+-- CreateTable
+CREATE TABLE "DeviceToken" (
+    "id" TEXT NOT NULL,
+    "token" TEXT NOT NULL,
+    "platform" TEXT NOT NULL,
+    "userId" TEXT,
+    "guestAccountId" TEXT,
+    "createdAt" TIMESTAMP(3) NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    "lastSeenAt" TIMESTAMP(3) NOT NULL DEFAULT CURRENT_TIMESTAMP,
+
+    CONSTRAINT "DeviceToken_pkey" PRIMARY KEY ("id")
+);
+
+-- CreateIndex
+CREATE UNIQUE INDEX "DeviceToken_token_key" ON "DeviceToken"("token");
+
+-- AddForeignKey
+ALTER TABLE "DeviceToken" ADD CONSTRAINT "DeviceToken_userId_fkey" FOREIGN KEY ("userId") REFERENCES "User"("id") ON DELETE CASCADE ON UPDATE CASCADE;
+
+-- AddForeignKey
+ALTER TABLE "DeviceToken" ADD CONSTRAINT "DeviceToken_guestAccountId_fkey" FOREIGN KEY ("guestAccountId") REFERENCES "GuestAccount"("id") ON DELETE CASCADE ON UPDATE CASCADE;

backend/prisma/schema.prisma

@@ -78,6 +78,7 @@ model User {
   memberships        Membership[]
   messages           ChatMessage[]
   chatParticipations ChatParticipant[]
+  deviceTokens       DeviceToken[]
 }
 
 /// Scopes a User's role to a specific Kc (and Gemeinde, if applicable).
@@ -107,10 +108,27 @@ model GuestAccount {
   lastName   String
   createdAt  DateTime @default(now())
 
-  kc         Kc            @relation(fields: [kcId], references: [id], onDelete: Cascade)
-  gemeinde   Gemeinde?     @relation(fields: [gemeindeId], references: [id], onDelete: Cascade)
-  messages   ChatMessage[]
-  teilnehmer Teilnehmer[]
+  kc           Kc            @relation(fields: [kcId], references: [id], onDelete: Cascade)
+  gemeinde     Gemeinde?     @relation(fields: [gemeindeId], references: [id], onDelete: Cascade)
+  messages     ChatMessage[]
+  teilnehmer   Teilnehmer[]
+  deviceTokens DeviceToken[]
+}
+
+/// A push-notification target (FCM registration token) bound to whoever
+/// registered it — a team `User` or a `GuestAccount`. Replicated so a
+/// notification can be sent from either server.
+model DeviceToken {
+  id             String   @id @default(cuid())
+  token          String   @unique
+  platform       String
+  userId         String?
+  guestAccountId String?
+  createdAt      DateTime @default(now())
+  lastSeenAt     DateTime @default(now())
+
+  user         User?         @relation(fields: [userId], references: [id], onDelete: Cascade)
+  guestAccount GuestAccount? @relation(fields: [guestAccountId], references: [id], onDelete: Cascade)
 }
 
 /// Invitation issued by a Gemeinde Verantwortliche/r so new Gemeinde Teamer

backend/src/app.module.ts

@@ -5,6 +5,7 @@ import { existsSync } from 'fs';
 import { join } from 'path';
 import { PrismaModule } from './prisma/prisma.module';
 import { MailModule } from './mail/mail.module';
+import { PushModule } from './push/push.module';
 import { AuthModule } from './auth/auth.module';
 import { KcModule } from './kc/kc.module';
 import { GemeindeModule } from './gemeinde/gemeinde.module';
@@ -35,6 +36,7 @@ const webRoot =
     }),
     PrismaModule,
     MailModule,
+    PushModule,
     SyncModule,
     AuthModule,
     KcModule,

backend/src/chat/chat.service.ts

@@ -4,16 +4,25 @@ import { PrismaClient } from '../prisma/prisma.module';
 import { AuthenticatedUser } from '../auth/authenticated-request';
 import { GuestJwtPayload } from '../auth/guest-auth.service';
 import { SyncService } from '../sync/sync.service';
+import { PushService } from '../push/push.service';
 
 export type ChatCaller =
   | { kind: 'user'; user: AuthenticatedUser }
   | { kind: 'guest'; guest: GuestJwtPayload };
 
+const CHANNEL_TITLES: Record<ChatChannelType, string> = {
+  [ChatChannelType.GEMEINDE_GRUPPE]: 'Gemeinde-Gruppe',
+  [ChatChannelType.DIREKT]: 'Direktnachricht',
+  [ChatChannelType.LT_UEBERGREIFEND]: 'Leitungsteam',
+  [ChatChannelType.BROADCAST]: 'Ankündigung',
+};
+
 @Injectable()
 export class ChatService {
   constructor(
     private readonly prisma: PrismaClient,
     private readonly sync: SyncService,
+    private readonly push: PushService,
   ) {}
 
   async createChannel(kcId: string, type: ChatChannelType, gemeindeId?: string) {
@@ -142,7 +151,7 @@ export class ChatService {
   }
 
   async sendMessage(channelId: string, caller: ChatCaller, body: string) {
-    await this.assertCanWrite(channelId, caller);
+    const channel = await this.assertCanWrite(channelId, caller);
     const message = await this.prisma.chatMessage.create({
       data: {
         channelId,
@@ -152,6 +161,20 @@ export class ChatService {
       },
     });
     await this.sync.capture('ChatMessage', SyncOperation.CREATE, message.id, message);
+
+    void this.push.notifyChannel(
+      channelId,
+      {
+        title: CHANNEL_TITLES[channel?.type ?? ChatChannelType.GEMEINDE_GRUPPE],
+        body: body.length > 140 ? `${body.slice(0, 137)}…` : body,
+        data: { channelId },
+      },
+      {
+        userId: caller.kind === 'user' ? caller.user.userId : null,
+        guestId: caller.kind === 'guest' ? caller.guest.guestId : null,
+      },
+    );
+
     return message;
   }
 

backend/src/push/dto/register-device.dto.ts

@@ -0,0 +1,16 @@
+import { IsIn, IsNotEmpty, IsString } from 'class-validator';
+
+export class RegisterDeviceDto {
+  @IsString()
+  @IsNotEmpty()
+  token!: string;
+
+  @IsIn(['web', 'android', 'ios'])
+  platform!: 'web' | 'android' | 'ios';
+}
+
+export class UnregisterDeviceDto {
+  @IsString()
+  @IsNotEmpty()
+  token!: string;
+}

backend/src/push/fcm-push.provider.ts

@@ -0,0 +1,110 @@
+import { readFileSync } from 'fs';
+import { Logger } from '@nestjs/common';
+import { ConfigService } from '@nestjs/config';
+import * as jwt from 'jsonwebtoken';
+import { PushNotification, PushProvider, PushResult } from './push-provider';
+
+interface ServiceAccount {
+  client_email: string;
+  private_key: string;
+  token_uri: string;
+}
+
+/// Firebase Cloud Messaging HTTP v1. Auth is a service-account JWT exchanged
+/// for an OAuth access token (no google-auth-library dependency — jsonwebtoken
+/// is already here). Delivery failures are logged and swallowed.
+export class FcmPushProvider implements PushProvider {
+  private readonly logger = new Logger('PushProvider');
+  private readonly projectId: string;
+  private readonly sa: ServiceAccount;
+  private accessToken: { value: string; expiresAt: number } | null = null;
+
+  constructor(config: ConfigService) {
+    this.projectId = config.getOrThrow<string>('FCM_PROJECT_ID');
+    const path = config.getOrThrow<string>('GOOGLE_APPLICATION_CREDENTIALS');
+    this.sa = JSON.parse(readFileSync(path, 'utf8')) as ServiceAccount;
+  }
+
+  async sendToTokens(tokens: string[], n: PushNotification): Promise<PushResult> {
+    if (tokens.length === 0) return { sent: 0, invalidTokens: [] };
+    let accessToken: string;
+    try {
+      accessToken = await this.getAccessToken();
+    } catch (err) {
+      this.logger.error(`FCM auth failed: ${(err as Error).message}`);
+      return { sent: 0, invalidTokens: [] };
+    }
+
+    const url = `https://fcm.googleapis.com/v1/projects/${this.projectId}/messages:send`;
+    const invalidTokens: string[] = [];
+    let sent = 0;
+
+    await Promise.all(
+      tokens.map(async (token) => {
+        try {
+          const res = await fetch(url, {
+            method: 'POST',
+            headers: {
+              Authorization: `Bearer ${accessToken}`,
+              'Content-Type': 'application/json',
+            },
+            body: JSON.stringify({
+              message: {
+                token,
+                notification: { title: n.title, body: n.body },
+                data: n.data,
+                webpush: { fcmOptions: {} },
+              },
+            }),
+          });
+          if (res.ok) {
+            sent += 1;
+          } else if (res.status === 404 || res.status === 400) {
+            invalidTokens.push(token);
+          } else {
+            this.logger.warn(`FCM send ${res.status}: ${await res.text()}`);
+          }
+        } catch (err) {
+          this.logger.warn(`FCM send error: ${(err as Error).message}`);
+        }
+      }),
+    );
+
+    return { sent, invalidTokens };
+  }
+
+  private async getAccessToken(): Promise<string> {
+    if (this.accessToken && this.accessToken.expiresAt > Date.now() + 60_000) {
+      return this.accessToken.value;
+    }
+    const now = Math.floor(Date.now() / 1000);
+    const assertion = jwt.sign(
+      {
+        iss: this.sa.client_email,
+        scope: 'https://www.googleapis.com/auth/firebase.messaging',
+        aud: this.sa.token_uri,
+        iat: now,
+        exp: now + 3600,
+      },
+      this.sa.private_key,
+      { algorithm: 'RS256' },
+    );
+    const res = await fetch(this.sa.token_uri, {
+      method: 'POST',
+      headers: { 'Content-Type': 'application/x-www-form-urlencoded' },
+      body: new URLSearchParams({
+        grant_type: 'urn:ietf:params:oauth:grant-type:jwt-bearer',
+        assertion,
+      }),
+    });
+    if (!res.ok) {
+      throw new Error(`token exchange ${res.status}: ${await res.text()}`);
+    }
+    const json = (await res.json()) as { access_token: string; expires_in: number };
+    this.accessToken = {
+      value: json.access_token,
+      expiresAt: Date.now() + json.expires_in * 1000,
+    };
+    return json.access_token;
+  }
+}

backend/src/push/log-push.provider.ts

@@ -0,0 +1,15 @@
+import { Logger } from '@nestjs/common';
+import { PushNotification, PushProvider, PushResult } from './push-provider';
+
+/// Default provider: doesn't send, just logs. Keeps the app working before
+/// FCM credentials are configured.
+export class LogPushProvider implements PushProvider {
+  private readonly logger = new Logger('PushProvider');
+
+  async sendToTokens(tokens: string[], n: PushNotification): Promise<PushResult> {
+    this.logger.log(
+      `[log-only] would push "${n.title}" to ${tokens.length} device(s): ${n.body}`,
+    );
+    return { sent: 0, invalidTokens: [] };
+  }
+}

backend/src/push/push-provider.ts

@@ -0,0 +1,20 @@
+/// Abstraction over the push backend. Default is a no-send provider that only
+/// logs; PUSH_PROVIDER=fcm switches to Firebase Cloud Messaging (HTTP v1).
+export interface PushNotification {
+  title: string;
+  body: string;
+  data?: Record<string, string>;
+}
+
+export interface PushResult {
+  sent: number;
+  /// Tokens FCM reported as permanently invalid — the caller prunes them.
+  invalidTokens: string[];
+}
+
+export interface PushProvider {
+  /// Best-effort: never throws for delivery problems.
+  sendToTokens(tokens: string[], notification: PushNotification): Promise<PushResult>;
+}
+
+export const PUSH_PROVIDER = Symbol('PUSH_PROVIDER');

backend/src/push/push.controller.ts

@@ -0,0 +1,29 @@
+import { Body, Controller, Post, Req, UseGuards } from '@nestjs/common';
+import { AuthGuard } from '@nestjs/passport';
+import { PushService } from './push.service';
+import { RegisterDeviceDto, UnregisterDeviceDto } from './dto/register-device.dto';
+// Import the util directly (not via chat.service) to keep the module graph acyclic.
+import { resolveChatCaller } from '../chat/caller.util';
+import { AuthenticatedRequest } from '../auth/authenticated-request';
+import { GuestJwtPayload } from '../auth/guest-auth.service';
+
+type PushRequest = AuthenticatedRequest & {
+  user?: AuthenticatedRequest['user'] | GuestJwtPayload;
+};
+
+@Controller('push')
+export class PushController {
+  constructor(private readonly push: PushService) {}
+
+  @Post('register')
+  @UseGuards(AuthGuard(['authentik', 'team', 'guest']))
+  register(@Body() dto: RegisterDeviceDto, @Req() req: PushRequest) {
+    return this.push.register(dto.token, dto.platform, resolveChatCaller(req.user!));
+  }
+
+  @Post('unregister')
+  @UseGuards(AuthGuard(['authentik', 'team', 'guest']))
+  unregister(@Body() dto: UnregisterDeviceDto) {
+    return this.push.unregister(dto.token);
+  }
+}

backend/src/push/push.module.ts

@@ -0,0 +1,27 @@
+import { Global, Module } from '@nestjs/common';
+import { ConfigService } from '@nestjs/config';
+import { PUSH_PROVIDER } from './push-provider';
+import { LogPushProvider } from './log-push.provider';
+import { FcmPushProvider } from './fcm-push.provider';
+import { PushService } from './push.service';
+import { PushController } from './push.controller';
+
+/// Global so ChatService can inject PushService. Provider defaults to
+/// log-only; PUSH_PROVIDER=fcm switches to Firebase Cloud Messaging.
+@Global()
+@Module({
+  controllers: [PushController],
+  providers: [
+    PushService,
+    {
+      provide: PUSH_PROVIDER,
+      inject: [ConfigService],
+      useFactory: (config: ConfigService) =>
+        config.get<string>('PUSH_PROVIDER') === 'fcm'
+          ? new FcmPushProvider(config)
+          : new LogPushProvider(),
+    },
+  ],
+  exports: [PushService],
+})
+export class PushModule {}

backend/src/push/push.service.ts

@@ -0,0 +1,151 @@
+import { Inject, Injectable, Logger } from '@nestjs/common';
+import { ChatChannelType, SyncOperation } from '@prisma/client';
+import { PrismaClient } from '../prisma/prisma.module';
+import { SyncService } from '../sync/sync.service';
+import type { ChatCaller } from '../chat/chat.service';
+import { PUSH_PROVIDER, PushNotification, PushProvider } from './push-provider';
+
+@Injectable()
+export class PushService {
+  private readonly logger = new Logger(PushService.name);
+
+  constructor(
+    private readonly prisma: PrismaClient,
+    private readonly sync: SyncService,
+    @Inject(PUSH_PROVIDER) private readonly provider: PushProvider,
+  ) {}
+
+  /// Upsert a device token for the current caller (team user or guest).
+  async register(token: string, platform: string, caller: ChatCaller) {
+    const owner =
+      caller.kind === 'user'
+        ? { userId: caller.user.userId, guestAccountId: null }
+        : { userId: null, guestAccountId: caller.guest.guestId };
+    const row = await this.prisma.deviceToken.upsert({
+      where: { token },
+      create: { token, platform, ...owner },
+      update: { platform, lastSeenAt: new Date(), ...owner },
+    });
+    await this.sync.capture('DeviceToken', SyncOperation.UPDATE, row.id, row);
+    return { ok: true };
+  }
+
+  async unregister(token: string) {
+    const existing = await this.prisma.deviceToken.findUnique({ where: { token } });
+    if (!existing) return { ok: true };
+    await this.prisma.deviceToken.delete({ where: { token } });
+    await this.sync.capture('DeviceToken', SyncOperation.DELETE, existing.id, {
+      id: existing.id,
+    });
+    return { ok: true };
+  }
+
+  /// Fan a chat message out as a push to everyone who can read the channel,
+  /// minus the sender. Best-effort — never throws into the caller.
+  async notifyChannel(
+    channelId: string,
+    notification: PushNotification,
+    exclude: { userId?: string | null; guestId?: string | null } = {},
+  ): Promise<void> {
+    try {
+      const channel = await this.prisma.chatChannel.findUnique({
+        where: { id: channelId },
+        include: { participants: { select: { userId: true } } },
+      });
+      if (!channel) return;
+
+      const { userIds, guestIds } = await this.audience(channel);
+      const tokens = await this.prisma.deviceToken.findMany({
+        where: {
+          OR: [
+            userIds.length ? { userId: { in: userIds } } : undefined,
+            guestIds.length ? { guestAccountId: { in: guestIds } } : undefined,
+          ].filter(Boolean) as object[],
+          NOT: {
+            OR: [
+              exclude.userId ? { userId: exclude.userId } : undefined,
+              exclude.guestId ? { guestAccountId: exclude.guestId } : undefined,
+            ].filter(Boolean) as object[],
+          },
+        },
+        select: { token: true },
+      });
+      if (tokens.length === 0) return;
+
+      const { invalidTokens } = await this.provider.sendToTokens(
+        tokens.map((t) => t.token),
+        notification,
+      );
+      if (invalidTokens.length) {
+        await this.prisma.deviceToken.deleteMany({
+          where: { token: { in: invalidTokens } },
+        });
+      }
+    } catch (err) {
+      this.logger.warn(`notifyChannel failed: ${(err as Error).message}`);
+    }
+  }
+
+  private async audience(channel: {
+    kcId: string;
+    type: ChatChannelType;
+    gemeindeId: string | null;
+    participants: { userId: string }[];
+  }): Promise<{ userIds: string[]; guestIds: string[] }> {
+    if (channel.type === ChatChannelType.DIREKT) {
+      return { userIds: channel.participants.map((p) => p.userId), guestIds: [] };
+    }
+
+    const ltUsers = await this.prisma.user.findMany({
+      where: {
+        OR: [
+          { isLeitungsteam: true },
+          { memberships: { some: { kcId: channel.kcId, role: 'LEITUNGSTEAM' } } },
+        ],
+      },
+      select: { id: true },
+    });
+    const ltIds = ltUsers.map((u) => u.id);
+
+    if (channel.type === ChatChannelType.LT_UEBERGREIFEND) {
+      return { userIds: ltIds, guestIds: [] };
+    }
+
+    if (channel.type === ChatChannelType.GEMEINDE_GRUPPE) {
+      const [members, guests] = await Promise.all([
+        this.prisma.membership.findMany({
+          where: {
+            kcId: channel.kcId,
+            gemeindeId: channel.gemeindeId,
+            status: 'ACTIVE',
+          },
+          select: { userId: true },
+        }),
+        this.prisma.guestAccount.findMany({
+          where: { kcId: channel.kcId, gemeindeId: channel.gemeindeId },
+          select: { id: true },
+        }),
+      ]);
+      return {
+        userIds: [...new Set([...ltIds, ...members.map((m) => m.userId)])],
+        guestIds: guests.map((g) => g.id),
+      };
+    }
+
+    // BROADCAST: everyone in the KC.
+    const [members, guests] = await Promise.all([
+      this.prisma.membership.findMany({
+        where: { kcId: channel.kcId, status: 'ACTIVE' },
+        select: { userId: true },
+      }),
+      this.prisma.guestAccount.findMany({
+        where: { kcId: channel.kcId },
+        select: { id: true },
+      }),
+    ]);
+    return {
+      userIds: [...new Set([...ltIds, ...members.map((m) => m.userId)])],
+      guestIds: guests.map((g) => g.id),
+    };
+  }
+}

backend/src/sync/sync.service.ts

@@ -18,6 +18,7 @@ const SYNCED_MODELS = [
   'File',
   'ChatChannel',
   'ChatMessage',
+  'DeviceToken',
 ] as const;
 export type SyncedModel = (typeof SYNCED_MODELS)[number];