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/app.module.ts

@@ -5,6 +5,7 @@ import { SearchModule } from '@modules/search';
 import { NotificationsModule } from '@modules/notifications';
 import { PaymentsModule } from '@modules/payments';
 import { SubscriptionsModule } from '@modules/subscriptions';
+import { AdminModule } from '@modules/admin';
 import { Module } from '@nestjs/common';
 import { APP_GUARD } from '@nestjs/core';
 import { CqrsModule } from '@nestjs/cqrs';
@@ -22,6 +23,7 @@ import { AppController } from './app.controller';
     NotificationsModule,
     PaymentsModule,
     SubscriptionsModule,
+    AdminModule,
 
     // ── Rate Limiting ──
     // Default: 60 requests per 60 seconds per IP