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.

states/buy.py

@@ -5,3 +5,8 @@ class SubscriptionStorage(StatesGroup):
     devices = State()
     duration = State()
     checkout = State()
+
+
+class BillingStorage(StatesGroup):
+    pending = State()
+    refresh = State()