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/handlers/user/trial_handler.py

@@ -7,7 +7,7 @@ from datetime import datetime
 from config.settings import Settings
 from bot.services.subscription_service import SubscriptionService
 from bot.services.panel_api_service import PanelApiService
-from bot.services.notification_service import notify_admin_new_trial
+from bot.services.notification_service import NotificationService
 from bot.keyboards.inline.user_keyboards import (
     get_trial_confirmation_keyboard,
     get_main_menu_inline_keyboard,
@@ -97,13 +97,8 @@ async def request_trial_confirmation_handler(
         )
         
         # Send notification to admin about new trial
-        await notify_admin_new_trial(
-            callback.bot,
-            settings,
-            i18n,
-            user_id,
-            end_date_obj,
-        )
+        notification_service = NotificationService(callback.bot, settings, i18n)
+        await notification_service.notify_trial_activation(user_id, end_date_obj)
     else:
         message_key_from_service = (
             activation_result.get("message_key", "trial_activation_failed")
@@ -264,13 +259,8 @@ async def confirm_activate_trial_handler(
             )
 
     if activation_result and activation_result.get("activated") and end_date_obj:
-        await notify_admin_new_trial(
-            callback.bot,
-            settings,
-            i18n,
-            user_id,
-            end_date_obj,
-        )
+        notification_service = NotificationService(callback.bot, settings, i18n)
+        await notification_service.notify_trial_activation(user_id, end_date_obj)
 
 
 @router.callback_query(F.data == "main_action:cancel_trial")