feat: update check (#561)

feat(update-check): add robust update check with interval support, state management, and CLI integration

- Implement version and interval-based update checks with configurable settings
- Add CLI command `kleinanzeigen-bot update-check` for manual checks
- Introduce state file with versioning, UTC timestamps, and migration logic
- Validate and normalize intervals (1d–4w) with fallback for invalid values
- Ensure correct handling of timezones and elapsed checks
- Improve error handling, logging, and internationalization (i18n)
- Add comprehensive test coverage for config, interval logic, migration, and CLI
- Align default config, translations, and schema with new functionality
- Improve help command UX by avoiding config/log loading for `--help`
- Update documentation and README with full feature overview

tests/unit/test_init.py

@@ -297,13 +297,11 @@ class TestKleinanzeigenBotConfiguration:
         test_bot.config_file_path = str(config_path)
 
         with patch.object(LOG, "warning") as mock_warning:
-            with pytest.raises(ValidationError) as exc_info:
-                test_bot.load_config()
-
+            test_bot.load_config()
             mock_warning.assert_called_once()
             assert config_path.exists()
-            assert "login.username" in str(exc_info.value)
-            assert "login.password" in str(exc_info.value)
+            assert test_bot.config.login.username == "changeme"  # noqa: S105 placeholder for default config, not a real username
+            assert test_bot.config.login.password == "changeme"  # noqa: S105 placeholder for default config, not a real password
 
     def test_load_config_validates_required_fields(self, test_bot:KleinanzeigenBot, test_data_dir:str) -> None:
         """Verify that config validation checks required fields."""