fix: Add scrollable container to ToolSelectorModal for small screens

- Add max-h-[90vh] and flex-col to modal content container
- Wrap tools grid in max-h-[50vh] overflow-y-auto container
- Add overscroll-contain for smooth scroll behavior on mobile
- Fixes issue where 21 PDF tools overflow viewport on small screens

backend/app/routes/removebg.py

@@ -38,7 +38,7 @@ def remove_bg_route():
 
     actor = resolve_web_actor()
     try:
-        assert_quota_available(actor)
+        assert_quota_available(actor, tool="remove-bg")
     except PolicyError as e:
         return jsonify({"error": e.message}), e.status_code