fix: Align NestJS entity columns with service expectations

Resolved 12 TypeScript compilation errors caused by mismatched column names between TypeORM entities and service layer.

Entity changes:
- NotificationsConfig: Renamed email_alerts_enabled → email_enabled, added email_address, standardized notification event column names (notify_on_start, notify_on_stop, notify_on_crash, etc.)
- ScheduledTask: Renamed is_active → is_enabled, added last_run timestamp
- TeamMember: Renamed accepted_at → joined_at to match service expectations
- Role: Added description column for custom role metadata

Service changes:
- JwtStrategy: Updated to reference joined_at instead of accepted_at

All services now compile cleanly against updated entity schemas.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend-nest/src/modules/auth/jwt.strategy.ts

@@ -83,7 +83,7 @@ export class JwtStrategy extends PassportStrategy(Strategy) {
         relations: ['license', 'role'],
       });
 
-      if (teamMember && teamMember.accepted_at) {
+      if (teamMember && teamMember.joined_at) {
         license = teamMember.license;
         role = teamMember.role;
       }