feat(backend): tolerate Authentik users without an email + verify against real SSO

Authentik accounts don't always have an email set (the test account
`hermes` doesn't). AuthentikStrategy / verifyAuthentikClaims no longer
reject those — `authentikEmail()` falls back to a stable
`<preferred_username|sub>@no-email.authentik` handle for the local User row,
and first/last name fall back to preferred_username/name.

Set AUTHENTIK_LEITUNGSTEAM_GROUP to the real group "KC-APP-LT".

Verified end to end against the live https://sso.konfi-castle.com with a
password-grant token for a KC-APP-LT member: backend accepts the RS256
token (JWKS + trailing-slash issuer), JIT-provisions the User, maps the
`groups` claim to isLeitungsteam=true, and POST /api/kc returns 201. Only
the in-browser redirect round-trip remains untested.

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

backend/src/auth/authentik.strategy.ts

@@ -7,13 +7,19 @@ import { Request } from 'express';
 import { PrismaClient } from '../prisma/prisma.module';
 import { SyncService } from '../sync/sync.service';
 import { AuthenticatedUser } from './authenticated-request';
-import { resolveOrProvisionAuthentikUser, toAuthenticatedUser } from './provision-user';
+import {
+  authentikEmail,
+  resolveOrProvisionAuthentikUser,
+  toAuthenticatedUser,
+} from './provision-user';
 
 interface AuthentikJwtPayload {
   sub: string;
   email?: string;
   given_name?: string;
   family_name?: string;
+  preferred_username?: string;
+  name?: string;
   groups?: string[];
 }
 
@@ -52,8 +58,8 @@ export class AuthentikStrategy extends PassportStrategy(Strategy, 'authentik') {
   }
 
   async validate(payload: AuthentikJwtPayload): Promise<AuthenticatedUser> {
-    if (!payload.email) {
-      throw new UnauthorizedException('Authentik token missing email claim');
+    if (!payload.sub) {
+      throw new UnauthorizedException('Authentik token missing subject');
     }
     const isLeitungsteam = (payload.groups ?? []).includes(this.leitungsteamGroup);
     const user = await resolveOrProvisionAuthentikUser(
@@ -61,8 +67,8 @@ export class AuthentikStrategy extends PassportStrategy(Strategy, 'authentik') {
       this.sync,
       {
         sub: payload.sub,
-        email: payload.email,
-        firstName: payload.given_name ?? '',
+        email: authentikEmail(payload),
+        firstName: payload.given_name ?? payload.preferred_username ?? payload.name ?? '',
         lastName: payload.family_name ?? '',
       },
       isLeitungsteam,

backend/src/auth/provision-user.ts

@@ -10,6 +10,18 @@ export interface AuthentikClaims {
   lastName: string;
 }
 
+/// Authentik users don't necessarily have an email set. Fall back to a stable,
+/// per-user placeholder so provisioning still has a unique handle for the row.
+export function authentikEmail(p: {
+  email?: string;
+  preferred_username?: string;
+  sub: string;
+}): string {
+  const e = p.email?.trim();
+  if (e) return e.toLowerCase();
+  return `${p.preferred_username?.trim() || p.sub}@no-email.authentik`.toLowerCase();
+}
+
 /// Placeholder kcId for the synthetic, global LEITUNGSTEAM membership. RolesGuard
 /// never compares it (LT short-circuits the KC check), it only needs to exist.
 export const GLOBAL_LT_KC_ID = '*';

backend/src/auth/token-verification.service.ts

@@ -10,6 +10,7 @@ import { GuestJwtPayload } from './guest-auth.service';
 import { TeamAuthService } from './team-auth.service';
 import {
   AuthentikClaims,
+  authentikEmail,
   resolveOrProvisionAuthentikUser,
   toAuthenticatedUser,
 } from './provision-user';
@@ -55,15 +56,22 @@ export class TokenVerificationService {
       email?: string;
       given_name?: string;
       family_name?: string;
+      preferred_username?: string;
+      name?: string;
       groups?: string[];
     };
-    if (!payload.sub || !payload.email) {
-      throw new UnauthorizedException('Authentik token missing subject or email');
+    const sub = payload.sub;
+    if (!sub) {
+      throw new UnauthorizedException('Authentik token missing subject');
     }
     return {
-      sub: payload.sub,
-      email: payload.email,
-      firstName: payload.given_name ?? '',
+      sub,
+      email: authentikEmail({
+        email: payload.email,
+        preferred_username: payload.preferred_username,
+        sub,
+      }),
+      firstName: payload.given_name ?? payload.preferred_username ?? payload.name ?? '',
       lastName: payload.family_name ?? '',
       isLeitungsteam: (payload.groups ?? []).includes(this.leitungsteamGroup),
     };