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/routers.py

@@ -0,0 +1,26 @@
+from aiogram import Router
+
+from bot.handlers.user import user_router_aggregate
+from bot.handlers import inline_mode
+from bot.handlers.admin import admin_router_aggregate
+from bot.filters.admin_filter import AdminFilter
+from config.settings import Settings
+
+
+def build_root_router(settings: Settings) -> Router:
+    root = Router(name="root")
+
+    # Public routers
+    root.include_router(user_router_aggregate)
+    root.include_router(inline_mode.router)
+
+    # Admin routers behind filter
+    admin_main_router = Router(name="admin_main_filtered_router")
+    admin_filter_instance = AdminFilter(admin_ids=settings.ADMIN_IDS)
+    admin_main_router.message.filter(admin_filter_instance)
+    admin_main_router.callback_query.filter(admin_filter_instance)
+    admin_main_router.include_router(admin_router_aggregate)
+    root.include_router(admin_main_router)
+
+    return root
+