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.

tests/test_repository_duty_range.py

@@ -1,4 +1,4 @@
-"""Tests for delete_duties_in_range and get_or_create_user_by_full_name."""
+"""Tests for delete_duties_in_range, get_or_create_user_by_full_name, name_manually_edited."""
 
 import pytest
 from sqlalchemy import create_engine
@@ -7,9 +7,11 @@ from sqlalchemy.orm import sessionmaker
 from duty_teller.db.models import Base, User
 from duty_teller.db.repository import (
     delete_duties_in_range,
+    get_or_create_user,
     get_or_create_user_by_full_name,
     get_duties,
     insert_duty,
+    update_user_display_name,
 )
 
 
@@ -47,6 +49,7 @@ def test_get_or_create_user_by_full_name_creates(session):
     assert u.id is not None
     assert u.full_name == "Новый Пользователь"
     assert u.telegram_user_id is None
+    assert u.name_manually_edited is True
 
 
 def test_get_or_create_user_by_full_name_returns_existing(session, user_a):
@@ -107,3 +110,88 @@ def test_get_duties_includes_duty_starting_on_last_day_of_range(session, user_a)
     assert len(rows) == 1
     assert rows[0][0].start_at == "2026-01-31T09:00:00Z"
     assert rows[0][1] == "User A"
+
+
+def test_get_or_create_user_overwrites_name_when_flag_false(session):
+    """When name_manually_edited is False, second get_or_create_user overwrites name."""
+    u1 = get_or_create_user(
+        session,
+        telegram_user_id=100,
+        full_name="First Name",
+        username="user1",
+        first_name="First",
+        last_name="Name",
+    )
+    assert u1.full_name == "First Name"
+    assert u1.name_manually_edited is False
+    u2 = get_or_create_user(
+        session,
+        telegram_user_id=100,
+        full_name="Second Name",
+        username="user2",
+        first_name="Second",
+        last_name="Name",
+    )
+    assert u2.id == u1.id
+    assert u2.full_name == "Second Name"
+    assert u2.first_name == "Second"
+    assert u2.last_name == "Name"
+    assert u2.username == "user2"
+
+
+def test_get_or_create_user_keeps_name_when_flag_true_updates_username(session):
+    """When name_manually_edited is True, get_or_create_user keeps name but updates username."""
+    u1 = get_or_create_user(
+        session,
+        telegram_user_id=200,
+        full_name="Custom Name",
+        username="old_username",
+        first_name="Custom",
+        last_name="Name",
+    )
+    u1.name_manually_edited = True
+    session.commit()
+    session.refresh(u1)
+    u2 = get_or_create_user(
+        session,
+        telegram_user_id=200,
+        full_name="Telegram Name",
+        username="new_username",
+        first_name="Telegram",
+        last_name="Name",
+    )
+    assert u2.id == u1.id
+    assert u2.full_name == "Custom Name"
+    assert u2.first_name == "Custom"
+    assert u2.last_name == "Name"
+    assert u2.username == "new_username"
+
+
+def test_update_user_display_name_sets_flag_then_get_or_create_user_keeps_name(session):
+    """update_user_display_name sets name and flag; get_or_create_user then does not overwrite name."""
+    get_or_create_user(
+        session,
+        telegram_user_id=300,
+        full_name="Original",
+        username="u3",
+        first_name="Original",
+        last_name=None,
+    )
+    updated = update_user_display_name(
+        session, 300, "Manual Name", first_name="Manual", last_name="Name"
+    )
+    assert updated is not None
+    assert updated.full_name == "Manual Name"
+    assert updated.name_manually_edited is True
+    u_after_sync = get_or_create_user(
+        session,
+        telegram_user_id=300,
+        full_name="From Telegram",
+        username="new_u3",
+        first_name="From",
+        last_name="Telegram",
+    )
+    assert u_after_sync.full_name == "Manual Name"
+    assert u_after_sync.first_name == "Manual"
+    assert u_after_sync.last_name == "Name"
+    assert u_after_sync.username == "new_u3"