Refactor notification handling and streamline router registration

- Replaced legacy notification functions with a unified NotificationService for better maintainability and clarity.
- Updated the main bot router registration to utilize a root router, simplifying the inclusion of user and admin routes.
- Removed unused middleware and helper functions to enhance code cleanliness and focus on essential components.
- Improved localization by adding new error messages for user interactions.

bot/middlewares/db_session.py

@@ -0,0 +1,40 @@
+import logging
+from typing import Callable, Dict, Any, Awaitable
+
+from aiogram import BaseMiddleware
+from aiogram.types import Update
+from sqlalchemy.orm import sessionmaker
+
+
+class DBSessionMiddleware(BaseMiddleware):
+
+    def __init__(self, async_session_factory: sessionmaker):
+        super().__init__()
+        self.async_session_factory = async_session_factory
+
+    async def __call__(
+        self,
+        handler: Callable[[Update, Dict[str, Any]], Awaitable[Any]],
+        event: Update,
+        data: Dict[str, Any],
+    ) -> Any:
+        if self.async_session_factory is None:
+            logging.critical("DBSessionMiddleware: async_session_factory is None!")
+            raise RuntimeError(
+                "async_session_factory not provided to DBSessionMiddleware"
+            )
+
+        async with self.async_session_factory() as session:
+            data["session"] = session
+            try:
+                result = await handler(event, data)
+
+                await session.commit()
+                return result
+            except Exception:
+                await session.rollback()
+                logging.error(
+                    "DBSessionMiddleware: Exception caused rollback.", exc_info=True
+                )
+                raise
+