✨ feat(admin): add user data dashboard for cross-project data visualization

Add comprehensive admin dashboard to view and manage user data across all projects:

Backend:
- Add admin endpoints to Chat, Todo, Contacts, Calendar, Picture, Zitare, Presi
- Each backend exposes GET/DELETE /api/v1/admin/user-data/:userId
- Service-to-service auth via X-Service-Key header

Aggregation (mana-core-auth):
- GET /api/v1/admin/users - Paginated user list with search
- GET /api/v1/admin/users/:userId/data - Aggregated data from all backends
- DELETE /api/v1/admin/users/:userId/data - GDPR deletion across all projects

Frontend (ManaCore web):
- New User Data tab in admin navigation
- User search page at /admin/user-data
- User detail page with ProjectDataCard components
- GDPR deletion dialog with email confirmation

Presi:
- Migrate user_id from UUID to TEXT for Better Auth compatibility
- Add SQL migration script

services/mana-core-auth/src/app.module.ts

@@ -13,6 +13,7 @@ import { AiModule } from './ai/ai.module';
 import { HealthModule } from './health/health.module';
 import { MetricsModule } from './metrics';
 import { AnalyticsModule } from './analytics';
+import { AdminModule } from './admin/admin.module';
 import { HttpExceptionFilter } from './common/filters/http-exception.filter';
 import { LoggerModule } from './common/logger';
 
@@ -39,6 +40,7 @@ import { LoggerModule } from './common/logger';
 		ReferralsModule,
 		SettingsModule,
 		TagsModule,
+		AdminModule,
 	],
 	providers: [
 		{