**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.

cbreader/settings/test.py

@@ -0,0 +1,24 @@
+"""Settings used by the test suite.
+
+In-memory SQLite so the tests do not need a running Postgres, and a scratch comic
+volume that the fixtures fill with generated archives.
+"""
+
+import os
+from pathlib import Path
+
+from cbreader.settings.base import *  # noqa: F403
+from cbreader.settings.base import BASE_DIR
+
+SECRET_KEY = 'test-secret-key'
+ALLOWED_HOSTS = ['*']
+
+DATABASES = {
+    'default': {
+        'ENGINE': 'django.db.backends.sqlite3',
+        'NAME': ':memory:',
+    }
+}
+
+COMIC_BOOK_VOLUME = Path(os.environ.get('COMIC_TEST_VOLUME', BASE_DIR / 'test_comics'))
+MEDIA_ROOT = BASE_DIR / 'test_media'