**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.

comic/tests/factories.py

@@ -0,0 +1,31 @@
+"""Helpers for creating comic files on disk."""
+
+import io
+import zipfile
+from pathlib import Path
+
+import pymupdf
+from PIL import Image
+
+
+def make_cbz(path: Path, pages: int = 3, metadata: bool = True) -> Path:
+    """Write a .cbz containing PNG pages and, optionally, a ComicInfo.xml."""
+    with zipfile.ZipFile(path, 'w') as archive:
+        for page in range(pages):
+            image = Image.new('RGB', (10, 10))
+            buffer = io.BytesIO()
+            image.save(buffer, format='PNG')
+            archive.writestr(f'page{page:02}.png', buffer.getvalue())
+        if metadata:
+            archive.writestr('ComicInfo.xml', '<ComicInfo><Title>Test</Title></ComicInfo>')
+    return path
+
+
+def make_pdf(path: Path, pages: int = 2) -> Path:
+    """Write a PDF with the given number of pages."""
+    document = pymupdf.open()
+    for _ in range(pages):
+        document.new_page(width=10, height=10)
+    document.save(path)
+    document.close()
+    return path