**Replace Flake8 with Ruff, refactor type hints, and enhance archive processing logic**

- Removed `flake8` and `flake8-annotations` from dependencies, replaced by `ruff` for linting.
- Introduced cleaner type hinting and modern Python annotations (PEP 604 style) across multiple modules.
- Moved archive processing to a dedicated helper (`comic.archives`) for improved maintainability.
- Updated and simplified logic for archive file retrieval, directory cleaning, and user access validation.
- Improved error handling and added support for user classification restrictions in API responses.

.gitignore

@@ -96,3 +96,10 @@ node_modules
 localhost-key.pem
 localhost.pem
 webpack-stats.json
+
+# Test artifacts
+.pytest_cache/
+test_comics/
+test_media/
+htmlcov/
+.coverage