Enhance private handlers structure and add database support

- Introduced a new `PrivateHandlers` class to encapsulate private message handling logic, improving organization and maintainability.
- Added new dependencies in `requirements.txt` for database support with `aiosqlite`.
- Updated the private handlers to utilize modular components for better separation of concerns and easier testing.
- Implemented error handling and logging for improved robustness in message processing.

helper_bot/handlers/private/__init__.py

@@ -1 +1,20 @@
-from .private_handlers import private_router
+"""Private handlers package for Telegram bot"""
+
+from .private_handlers import private_router, create_private_handlers, PrivateHandlers
+from .services import BotSettings, UserService, PostService, StickerService
+from .constants import FSM_STATES, BUTTON_TEXTS, ERROR_MESSAGES
+from .decorators import error_handler
+
+__all__ = [
+    'private_router',
+    'create_private_handlers', 
+    'PrivateHandlers',
+    'BotSettings',
+    'UserService',
+    'PostService', 
+    'StickerService',
+    'FSM_STATES',
+    'BUTTON_TEXTS',
+    'ERROR_MESSAGES',
+    'error_handler'
+]