refactor: change Face Trace display from 'Face{id}' to 'FS{id}'

Display format clarification:
- Frame: F{number} (e.g., F333)
- Face Trace: FS{number} (e.g., FS233)

Internal data remains: trace_id = 233 (integer)
Display text: FS233 (Face Sequence)

Changes:
- Line 143: Face Detail Modal display
- Line 262: Cluster strip fallback display
- Line 264: Cluster strip label

Reason:
- FS = Face Sequence (clear meaning)
- Avoid confusion with Frame (F)
- Separation of concerns: internal ID vs display text

src/views/PeopleView.vue

@@ -140,7 +140,7 @@
           </div>
           <div class="ms-face-detail-info">
             <div class="ms-face-detail-title">
-              <span class="ms-face-trace-id">{{ faceDetailModal.candidate?.file_uuid }}:Face{{ faceDetailModal.candidate?.trace_id }}</span>
+              <span class="ms-face-trace-id">{{ faceDetailModal.candidate?.file_uuid }}:FS{{ faceDetailModal.candidate?.trace_id }}</span>
             </div>
             <div class="ms-face-detail-row">
               <span class="ms-face-detail-label">{{ t('people.face_detail.frame_number') }}</span>
@@ -259,9 +259,9 @@
               </div>
               <div class="ms-ppl-strip-face-img">
                 <img v-if="faceThumbsCache[thumbTraceKey(t)]" :src="faceThumbsCache[thumbTraceKey(t)]" alt="" loading="lazy">
-                <div v-else style="width:100%;height:100%;display:flex;align-items:center;justify-content:center;background:#eef2ff;color:#6366f1;font-size:10px;font-weight:600;border-radius:8px;">Face{{ t.trace_id }}</div>
+                <div v-else style="width:100%;height:100%;display:flex;align-items:center;justify-content:center;background:#eef2ff;color:#6366f1;font-size:10px;font-weight:600;border-radius:8px;">FS{{ t.trace_id }}</div>
               </div>
-              <div class="ms-ppl-strip-trace-label">Face{{ t.trace_id }}<span class="ms-ppl-strip-group-name">{{ clusterDetailModal.cluster?.name }}</span></div>
+              <div class="ms-ppl-strip-trace-label">FS{{ t.trace_id }}<span class="ms-ppl-strip-group-name">{{ clusterDetailModal.cluster?.name }}</span></div>
             </div>
           </div>
           <button class="ms-ppl-strip-arrow" :disabled="clusterStripPage >= clusterStripTotalPages" @click="clusterStripPage++">›</button>