Add file deletion detection, WebKit improvements, and bug fixes

- Add FileExternallyDeletedEvent with UI indicator in tabs for deleted files
- Set minimum height (300px) for editors container
- Add Developer Tools to WebKit context menu
- Fix DnD URI handling when uris list is empty
- Fix buffer replacement using freeze_notify and proper bounds handling
- Move webkit_ui_settings to new path
- Remove <change_me> placeholders from APP_NAME and user config

src/libs/dto/code/__init__.py

@@ -6,6 +6,8 @@
 from .code_event import CodeEvent
 from .register_provider_event import RegisterProviderEvent
 from .register_command_event import RegisterCommandEvent
+from .file_externally_modified_event  import FileExternallyModifiedEvent
+from .file_externally_deleted_event  import FileExternallyDeletedEvent
 
 from .get_new_command_system_event import GetNewCommandSystemEvent
 from .request_completion_event import RequestCompletionEvent