lint: replace no-op flake8 script with gating ruff check, fix findings

backend/api/videos.py

@@ -6,34 +6,33 @@ from datetime import date
 from typing import Annotated, Optional
 
 from fastapi import APIRouter, Depends, HTTPException, Query, Request, status
-from fastapi.responses import FileResponse, Response, StreamingResponse
+from fastapi.responses import FileResponse, Response
 from redis import Redis
 from rq import Queue
 from sqlalchemy.orm import Session
 
-from backend.db.session import get_db
-from backend.db.models import Photo, User
 from backend.api.auth import get_current_user_with_id
+from backend.db.models import Photo, User
+from backend.db.session import get_db
 from backend.schemas.videos import (
-    ListVideosResponse,
-    VideoListItem,
-    PersonInfo,
-    VideoPeopleResponse,
-    VideoPersonInfo,
     IdentifyVideoRequest,
     IdentifyVideoResponse,
+    ListVideosResponse,
+    PersonInfo,
     RemoveVideoPersonResponse,
+    VideoListItem,
+    VideoPeopleResponse,
+    VideoPersonInfo,
     WebPlaybackPrepareResponse,
     WebPlaybackStatusResponse,
 )
+from backend.services.thumbnail_service import get_video_thumbnail_path
 from backend.services.video_service import (
-    list_videos_for_identification,
     get_video_people,
     identify_person_in_video,
+    list_videos_for_identification,
     remove_person_from_video,
-    get_video_people_count,
 )
-from backend.services.thumbnail_service import get_video_thumbnail_path
 from backend.services.web_video_service import (
     expire_web_playable_if_stale,
     get_web_playback_status_dict,
@@ -314,8 +313,9 @@ def get_video_file(
     db: Session = Depends(get_db),
 ):
     """Serve video file for playback with range request support."""
-    import os
     import mimetypes
+    import os
+
     from starlette.responses import FileResponse
     
     # Verify video exists