Fix ~790 basedpyright errors across the test suite:
- Type stub subclasses of real production classes with super().__init__()
- Add missing generic type arguments and Dict[str, Any] annotations
- Add None guards before subscript/member access
- Adapt tests to production API changes (removed dead handlers,
PersistentModelCache.get_default, _i18n_filter_added location)
fix(example_images_download_manager): re-raise specific exception on download error
refactor(usage_stats): define constants locally to avoid conditional imports
test(example_images_download_manager): update exception handling in download tests
test(example_images_file_manager): differentiate between os.startfile and subprocess.Popen in tests
test(example_images_paths): ensure valid example images root with single-library mode
test(usage_stats): use string literals for metadata payload to avoid conditional imports
