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/filters/admins.py

@@ -0,0 +1,8 @@
+from aiogram.filters import Filter
+
+from config import settings
+
+
+class AdminFilter(Filter):
+    async def __call__(self, event) -> bool:
+        return event.from_user.id in settings.admins