feat(admin): add Admin module with moderation, user mgmt, and dashboard

- Commands: ApproveListing, RejectListing, BanUser, AdjustSubscription
- Queries: GetModerationQueue, GetDashboardStats, GetRevenueStats
- Admin-only guards via @Roles('ADMIN') on all endpoints
- Prisma-based admin query repository for dashboard aggregations
- 14 unit tests covering all command handlers and query handlers
- Added activate() method to UserEntity for unban support

Co-Authored-By: Paperclip <noreply@paperclip.ing>

apps/api/src/modules/auth/domain/entities/user.entity.ts

@@ -85,4 +85,9 @@ export class UserEntity extends AggregateRoot<string> {
     this._isActive = false;
     this.updatedAt = new Date();
   }
+
+  activate(): void {
+    this._isActive = true;
+    this.updatedAt = new Date();
+  }
 }