feat(viewer): UI-02 heart particles, interaction notices, share and download

Task 5 (V05 §5.4/§6): decorative heart particles on the lightbox stage
(local like clicks + others' WS bursts for the current photo), compact
cross-photo interaction notices above the action bar (click to locate),
navigator.share-first share orchestration with clipboard fallback for
album and photo deep links (lang param), and download failures attributed
to the photo that triggered them. Self-echo dedup stays in the realtime
router (own batches never produce particles/notices); particles cap at
12 with visibility/unmount cleanup and are suppressed under reduced
motion; notices cap at 3 with ~4s auto-dismiss and throttled SR summary.

Co-Authored-By: Claude Code <noreply@anthropic.com>

apps/viewer/src/pages/ActivityPage.vue

@@ -184,6 +184,17 @@ const currentPhoto = computed(() => {
   return sequence.photos.find((photo) => photo.photoId === lightboxPhotoId.value) ?? null;
 });
 
+/** 当前照片分享深链（V05 §5.4）：/a/:token/p/:photoId + lang 参数（当前 UI
+ * 语言），始终分享观众端路由——不分享 OSS 签名 URL。 */
+const photoShareUrl = computed(() => {
+  if (lightboxPhotoId.value === null) return undefined;
+  const href = router.resolve({
+    name: 'activity-photo',
+    params: { token: token.value, photoId: lightboxPhotoId.value },
+  }).href;
+  return `${href}?lang=${locale.value}`;
+});
+
 /** 下载控制器（P4a Task 4）：开关来自相册载荷，当前照片随大图键控。 */
 const download = useDownload({
   token,
@@ -344,19 +355,24 @@ onBeforeUnmount(() => {
       <PhotoFeed :sequence="sequence" :likes="likes" @open="openFromFeed" />
     </template>
 
-    <!-- 大图查看器（Task 8）：当前照片以 photoId 键控（v-model）。 -->
+    <!-- 大图查看器（Task 8）：当前照片以 photoId 键控（v-model）。V05 新增：
+         相册标题/照片深链（navigator.share）与实时气泡（粒子/互动提示分层）。 -->
     <PhotoLightbox
       v-if="lightboxPhotoId !== null && currentPhoto !== null"
       v-model:photo-id="lightboxPhotoId"
       :sequence="sequence"
       :likes="likes"
       :download="download"
+      :album-title="album !== null ? album.translation.title : undefined"
+      :share-url="photoShareUrl"
+      :like-bubbles="realtime.bubbles"
       @removed="onPhotoRemoved"
       @close="closeLightbox"
     />
 
-    <!-- 他人点赞气泡（Task 10）：点击定位打开该照片大图。 -->
-    <LikeBubbles :bubbles="realtime.bubbles" @open="openFromFeed" />
+    <!-- 他人点赞气泡（Task 10）：点击定位打开该照片大图。大图打开期间改由
+         查看器内互动提示承载（§6.2：避免页面级气泡被模态框盖住或遮住下载）。 -->
+    <LikeBubbles :bubbles="lightboxPhotoId === null ? realtime.bubbles : []" @open="openFromFeed" />
 
     <!-- 照片下线轻提示（大图 404 刷新 / WS hidden/deleted 推送移除时）。 -->
     <p v-if="photoRemovedNotice" class="removed-notice" role="status">{{ t('viewer.photoRemoved') }}</p>