feat: add subscription and transaction repositories

- Implemented SubscriptionRepository with methods to get, create, and update subscriptions.
- Added BalanceTXRepository for creating and retrieving balance transactions.
- Introduced a test script for simulating Pally webhook for local testing.

bot/handlers/billing.py

@@ -29,6 +29,7 @@ async def pally_init(
     await state.clear()
 
     ctx.provider = BillingProviders.PALLY
+    ctx.amount = int(ctx.amount)
 
     await cb.message.edit_text(
         BILL_CREATION.format(amount=ctx.amount, provider=ctx.provider.value.title())