Improve History playback after camera audio dropouts (#24793)

* skip vod clips that start after their audio ends

When a camera's audio dropped out, a recording segment could end its audio early. If a playback range started past that point in the segment, nginx-vod saw no audio track in the first clip, failed the whole range with a track count mismatch, and left the player spinning for up to an hour of footage. Recording now stores each segment's audio length alongside its keyframe index, from the same ffprobe pass, and plan_clip skips a clip whose window starts at or after its audio ends when the range has other clips. A range made of only that clip still plays video-only, and legacy rows without the new column are unchanged.

* keep audio skip consistent with playback

Clips were skipped even when the range would be served video-only, and seeking into a skipped span landed on later footage. The skip now only applies when every row in the range carries audio, and seeks inside a zero-duration span land on the next clip.

web/src/utils/videoUtil.ts

@@ -61,6 +61,12 @@ export function calculateSeekPosition(
       return false;
     }
 
+    // skipped clips have no playlist media, so a seek inside one lands on
+    // the next clip that plays
+    if (segment.duration === 0) {
+      return true;
+    }
+
     // playlist duration exceeds wall length when the clip carries
     // keyframe back-snap lead-in
     const wallLength = segment.end_time - segment.start_time;