feat: Face Filter 自動保存（500ms 防抖 + 離開頁面自動保存）

src/composables/useFaceFilter.ts

@@ -234,6 +234,9 @@ export function useFaceFilter() {
   const singleFrameSettingsError = ref<string | null>(null);
   const singleFrameSettingsModified = ref(false);
   
+  const currentFileUuid = ref<string | null>(null);
+  let autoSaveTimer: ReturnType<typeof setTimeout> | null = null;
+  
   // Computed stats
   const stats = computed(() => ({
     total: allFaces.value.length,
@@ -406,6 +409,7 @@ export function useFaceFilter() {
     singleFrameSettingsError.value = null;
     
     try {
+      currentFileUuid.value = fileUuid;
       const profile = await getFileProfile(fileUuid);
       singleFrameSettings.value = {
         single_frame_trace_vlm_enabled: profile.face_filter.single_frame_trace_vlm_enabled ?? true,
@@ -441,6 +445,29 @@ export function useFaceFilter() {
     }
   }
   
+  function autoSaveSettings() {
+    if (autoSaveTimer) {
+      clearTimeout(autoSaveTimer);
+    }
+    
+    autoSaveTimer = setTimeout(async () => {
+      if (currentFileUuid.value && singleFrameSettingsModified.value) {
+        const success = await saveSingleFrameSettings(currentFileUuid.value);
+        if (!success) {
+          console.error('Auto-save failed for single frame settings');
+        }
+      }
+      autoSaveTimer = null;
+    }, 500);
+  }
+  
+  function cleanupAutoSave() {
+    if (autoSaveTimer) {
+      clearTimeout(autoSaveTimer);
+      autoSaveTimer = null;
+    }
+  }
+  
   function resetSingleFrameSettings() {
     singleFrameSettings.value = {
       single_frame_trace_vlm_enabled: true,
@@ -449,10 +476,12 @@ export function useFaceFilter() {
       single_trace_group_filter_enabled: true,
     };
     singleFrameSettingsModified.value = true;
+    autoSaveSettings();
   }
   
   function markSingleFrameSettingsModified() {
     singleFrameSettingsModified.value = true;
+    autoSaveSettings();
   }
   
   return {
@@ -470,6 +499,7 @@ export function useFaceFilter() {
     singleFrameSettingsLoading,
     singleFrameSettingsError,
     singleFrameSettingsModified,
+    currentFileUuid,
     
     // Actions
     initialize,
@@ -484,6 +514,7 @@ export function useFaceFilter() {
     saveSingleFrameSettings,
     resetSingleFrameSettings,
     markSingleFrameSettingsModified,
+    cleanupAutoSave,
     
     // API helpers (exposed for direct use)
     fetchFaces,