feat: Implement payment notification system and API structure

- Added notifications for successful payments in `api/core/notifications.py`.
- Created main API entry point in `api/main.py` with FastAPI integration.
- Established routing structure in `api/routes/__init__.py` and `api/routes/pally.py` for handling payment callbacks.
- Developed billing handlers in `bot/handlers/billing.py` and `bot/handlers/buy.py` for subscription management.
- Introduced state management for user interactions in `bot/states/`.
- Created user interface elements in `bot/keyboards/` for navigation and payment processing.
- Set up middleware for dependency injection in `bot/middlewares/di.py`.
- Added support for user commands and interactions in `bot/handlers/common.py` and `bot/handlers/support.py`.
- Implemented logging and error handling throughout the bot's functionality.
- Created entry point script for API server in `entrypoints/api.sh`.

bot/handlers/referals.py

@@ -0,0 +1,28 @@
+from aiogram import F, Router
+from aiogram.fsm.context import FSMContext
+from aiogram.types import CallbackQuery
+from aiogram.utils.deep_linking import create_start_link
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from bot.keyboards.client import referals_kb
+from bot.texts import REFERALS_MENU
+from misc.utils import format_share_deep_link
+from schemas.di import DependenciesDTO
+
+router = Router()
+
+
+@router.callback_query(F.data == "referal")
+async def referal_menu(
+    cb: CallbackQuery, state: FSMContext, session: AsyncSession, deps: DependenciesDTO
+):
+    await state.clear()
+
+    user = await deps.user_repository.get_user_by_id(session, cb.from_user.id)
+    referal_link = await create_start_link(cb.bot, f"ref_{user.id}", encode=True)
+    share_link = format_share_deep_link(referal_link)
+
+    await cb.message.edit_text(
+        REFERALS_MENU.format(balance=user.balance, link=referal_link),
+        reply_markup=referals_kb(share_link),
+    )