feat(videos): add manual Convert button per MOV file on Pi

- New POST /api/local-video/convert route triggers queue_convert(force=True)
- queue_convert() now returns True/False/None and accepts force param
  to bypass the auto-convert toggle (manual always works)
- Convert button shown for non-MP4, non-converting files in video list
- Clicking spins the button and refreshes list after 1s to show badge

Co-authored-by: Copilot <[email protected]>

app.py

@@ -176,6 +176,17 @@ def local_video_delete():
     }
     return jsonify(summary), status_codes.get(summary["status"], 409)
 
+@app.route('/api/local-video/convert', methods=['POST'])
+def local_video_convert():
+    body = request.get_json(silent=True) or {}
+    path = body.get("path", "")
+    if not path:
+        return jsonify({"status": "invalid_path", "message": "No path provided."}), 400
+    queued = app_video.queue_convert(path, force=True)
+    if queued is False:
+        return jsonify({"status": "busy", "message": "Already converting."}), 409
+    return jsonify({"status": "started"})
+
 @app.route('/api/upload/status')
 def upload_status():
     return jsonify(app_upload.get_status())