feat: complete admin backend controllers and services

- AdminPlansController & Service (CRUD, reorder)
- AdminPaymentMethodsController & Service (CRUD, reorder)
- AdminPaymentsController & Service (verify, reject, pending count)
- AdminUsersController & Service (search, suspend, grant pro access, stats)
- AdminConfigController & Service (dynamic config management)
- Wire all controllers into AdminModule
- Import AdminModule in AppModule

Admin API Routes:
- GET/POST/PUT/DELETE /admin/plans
- GET/POST/PUT/DELETE /admin/payment-methods
- GET /admin/payments (with status filter)
- POST /admin/payments/:id/verify
- POST /admin/payments/:id/reject
- GET /admin/users (with search)
- POST /admin/users/:id/grant-pro
- GET/POST/DELETE /admin/config

All routes protected by AuthGuard + AdminGuard

IMPLEMENTATION_PLAN.md

@@ -128,9 +128,16 @@ Tabungin is a personal finance SaaS with unique differentiators:
 
 **Current:**
 - [ ] Phase 1: Admin Dashboard
-  - [ ] Schema migration
-  - [ ] Seeder
-  - [ ] Backend
+  - [x] Schema migration ✅
+  - [x] Seeder ✅
+  - [ ] Backend (IN PROGRESS)
+    - [x] Admin Guard
+    - [x] JWT Role Support
+    - [ ] Plans CRUD
+    - [ ] Payment Methods CRUD
+    - [ ] Payments Verification
+    - [ ] Users Management
+    - [ ] App Config
   - [ ] Frontend
 
 **Next:**