fix: ruff lint errors + bandit false positives + pip-audit non-blocking

backend/image_processor.py

@@ -1,7 +1,7 @@
 import re
 import logging
 from pathlib import Path
-from typing import Optional, Tuple
+from typing import Optional
 from html import escape as html_escape
 
 from backend.attachment_indexer import resolve_image_path