feat: add name_manually_edited field to User model and update related functionality

- Introduced a new boolean column `name_manually_edited` in the `users` table to control whether user names are overwritten during synchronization with Telegram.
- Updated the `get_or_create_user` function to respect the `name_manually_edited` flag, ensuring names are only updated when the flag is false.
- Implemented a new function `update_user_display_name` to allow manual updates of user names while setting the `name_manually_edited` flag to true.
- Enhanced unit tests to cover the new functionality and ensure correct behavior of name handling based on the `name_manually_edited` flag.

duty_teller/db/__init__.py

@@ -21,6 +21,7 @@ from duty_teller.db.repository import (
     get_duties,
     insert_duty,
     set_user_phone,
+    update_user_display_name,
 )
 
 __all__ = [
@@ -42,6 +43,7 @@ __all__ = [
     "get_duties",
     "insert_duty",
     "set_user_phone",
+    "update_user_display_name",
     "init_db",
 ]