Refactor bot handlers and keyboards; implement admin features

- Removed unused prehandling, referrals, support, and states files.
- Updated admin and client handlers to improve structure and functionality.
- Introduced admin filters and routers for better access control.
- Added new billing and deposit functionalities for client interactions.
- Enhanced keyboard layouts for admin and client menus.
- Implemented promotion handling for admin users.
- Updated configuration to include admin settings.
- Improved utility functions for quote fetching and menu text building.
- Added common handlers for undefined commands and message deletions.

bot/handlers/client/__init__.py

@@ -0,0 +1,15 @@
+from .billing import router as billing_router
+from .buy import router as buy_router
+from .deposit import router as deposit_router
+from .menus import router as menus_router
+from .referals import router as referal_router
+from .support import router as support_router
+
+routers = [
+    referal_router,
+    billing_router,
+    deposit_router,
+    menus_router,
+    support_router,
+    buy_router,
+]