Fix bugs, convert thumbnail to png, add context menu

backend/app/auth/session.py

@@ -0,0 +1,49 @@
+"""Session token generation and validation."""
+
+from typing import Any
+from fastapi import Response
+from itsdangerous import URLSafeTimedSerializer, BadSignature, SignatureExpired
+
+from app.config import settings
+
+def get_serializer() -> URLSafeTimedSerializer:
+    """Return a configured URLSafeTimedSerializer."""
+    return URLSafeTimedSerializer(settings.SECRET_KEY)
+
+def create_session(response: Response, user_id: int = 1) -> None:
+    """Create a new session token and set it as an HTTP-only cookie."""
+    serializer = get_serializer()
+    token = serializer.dumps({"user_id": user_id})
+    
+    response.set_cookie(
+        key=settings.COOKIE_NAME,
+        value=token,
+        max_age=settings.COOKIE_MAX_AGE_SECONDS,
+        secure=settings.COOKIE_SECURE,
+        httponly=True,
+        samesite="lax",
+    )
+
+def clear_session(response: Response) -> None:
+    """Clear the session cookie."""
+    response.delete_cookie(
+        key=settings.COOKIE_NAME,
+        secure=settings.COOKIE_SECURE,
+        httponly=True,
+        samesite="lax",
+    )
+
+def verify_session(token: str) -> int | None:
+    """
+    Verify the session token.
+    Returns the user_id if valid, or None if invalid/expired.
+    """
+    serializer = get_serializer()
+    try:
+        data: dict[str, Any] = serializer.loads(
+            token, 
+            max_age=settings.COOKIE_MAX_AGE_SECONDS
+        )
+        return data.get("user_id")
+    except (BadSignature, SignatureExpired):
+        return None