feat: implement billing system with Pally integration

- Added billing models and repository for handling bills.
- Introduced BillingService to manage payment initiation and bill creation.
- Updated user service to remove ticket-related functionality.
- Refactored settings to include new billing-related fields.
- Removed ticket-related handlers and schemas.
- Added new billing handlers for processing payments.
- Updated database schema with new bills table and status enum.
- Enhanced utility functions to calculate prices considering discounts.
- Introduced prehandling for non-private messages.
- Updated main application to initialize new billing services and repositories.

handlers/__init__.py

@@ -1,8 +1,19 @@
 from .ads import router as ads_router
+from .billing import router as billing_router
 from .buy import router as buy_router
 from .common import router as common_router
 from .menus import router as menus_router
+from .prehandling import router as prehandling_router
 from .referals import router as referal_router
 from .support import router as support_router
 
-routers = [referal_router, menus_router, ads_router, support_router, buy_router, common_router]
+routers = [
+    prehandling_router,
+    referal_router,
+    billing_router,
+    menus_router,
+    ads_router,
+    support_router,
+    buy_router,
+    common_router,
+]