feat: initialize backend with NestJS, PostgreSQL, and Prisma

- Add package.json for backend dependencies and scripts.
- Create Prisma schema for multi-tenant event management.
- Implement main application module and configure global settings.
- Develop authentication module with JWT and Authentik integration.
- Create DTOs for guest account creation and KC management.
- Implement role-based access control with custom guards and decorators.
- Add services and controllers for managing KCs and guest accounts.
- Set up global validation and CORS in the main application entry point.
- Establish Prisma module for database access throughout the application.
- Document project plan and architecture for multi-tenant platform.

backend/src/auth/auth.module.ts

@@ -0,0 +1,23 @@
+import { Module } from '@nestjs/common';
+import { ConfigService } from '@nestjs/config';
+import { JwtModule } from '@nestjs/jwt';
+import { PassportModule } from '@nestjs/passport';
+import { AuthController } from './auth.controller';
+import { GuestAuthService } from './guest-auth.service';
+import { AuthentikStrategy } from './authentik.strategy';
+
+@Module({
+  imports: [
+    PassportModule,
+    JwtModule.registerAsync({
+      inject: [ConfigService],
+      useFactory: (config: ConfigService) => ({
+        secret: config.getOrThrow<string>('GUEST_JWT_SECRET'),
+        signOptions: { expiresIn: '12h' },
+      }),
+    }),
+  ],
+  controllers: [AuthController],
+  providers: [GuestAuthService, AuthentikStrategy],
+})
+export class AuthModule {}