Rename metadata key to frame_timestamps

Updates the recording metadata schema in `video_recorder.py` by renaming `hardware_frame_timestamps` to `frame_timestamps`. This aligns timestamp data with a more general key name while preserving the same underlying values.

Author: C-Achard

dlclivegui/services/video_recorder.py

@@ -564,7 +564,7 @@ def _save_timestamps(self) -> None:
                     },
                     "hardware_timestamp": hardware_timestamp_source,
                 },
-                "hardware_frame_timestamps": frame_timestamps,
+                "frame_timestamps": frame_timestamps,
                 "start_time": software_timestamps[0] if software_timestamps else None,
                 "end_time": software_timestamps[-1] if software_timestamps else None,
                 "duration_seconds": (