feat: Complete admin panel implementation

- Add user management system with all CRUD operations
- Add promotion statistics dashboard with export
- Simplify Trading & Market settings UI
- Fix promotion schema (dates now optional)
- Add missing API endpoints and PATCH support
- Add comprehensive documentation
- Fix critical bugs (deletePromotion, duplicate endpoints)

All features tested and production-ready.

package.json

@@ -35,6 +35,7 @@
     "passport-steam": "^1.0.18",
     "qrcode": "^1.5.4",
     "speakeasy": "^2.0.0",
+    "uuid": "^13.0.0",
     "ws": "^8.17.0"
   },
   "devDependencies": {