fix: enforce frame-based positioning across all video playback

Core Principle: Frame is the only standard

Changes:
- VideoPlayer: Add startFrame/endFrame props
- VideoPlayer: Use frame parameters in simple playback path
- SearchView: Remove frame/time conversion (stop using fps = 24)
- PeopleView: Pass frames directly instead of time
- PersonDetailView: Pass frames directly instead of time

All video streams now use startFrame/endFrame API parameters.
Time conversion only happens in VideoPlayer internals for UI display.

Ref: frame-based positioning standards research

src/views/PeopleView.vue

@@ -1060,8 +1060,8 @@ async function playClusterVideo() {
     
     currentVideo.value = {
       fileUuid,
-      startTime: firstTrace ? (firstTrace.start_frame / fps) : 0,
-      endTime: lastTrace ? (lastTrace.end_frame / fps) : 30,
+      startFrame: firstTrace ? firstTrace.start_frame : 0,
+      endFrame: lastTrace ? lastTrace.end_frame : 30,
       title: `${getFileName(fileUuid)} - ${c.name}`,
     }
     clusterVideoTraces.value = allClusterTraces
@@ -1083,8 +1083,8 @@ async function playClusterTraceVideo(trace: any) {
     
     currentVideo.value = {
       fileUuid,
-      startTime: startFrame / fps,
-      endTime: endFrame / fps,
+      startFrame: startFrame,
+      endFrame: endFrame,
       title: `${getFileName(fileUuid)} - F${trace.trace_id}`,
     }
     clusterVideoTraces.value = [{