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.

repositories/bills.py

@@ -0,0 +1,25 @@
+from sqlalchemy import select
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from db.models.bills import Bill, BillStatus
+
+
+class BillsRepository:
+    async def get_bill_by_id(self, session: AsyncSession, bill_id: int) -> Bill | None:
+        stmt = select(Bill).where(Bill.id == bill_id)
+        res = await session.execute(stmt)
+
+        return res.scalar_one_or_none()
+
+    async def create(
+        self,
+        session: AsyncSession,
+        *,
+        creator_id: int,
+        amount: int,
+        status: BillStatus | None = BillStatus.NEW,
+    ) -> Bill:
+        bill = Bill(creator_id=creator_id, amount=amount, status=status)
+        session.add(bill)
+        await session.commit()
+        return bill