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/__tests__/photo-action-bar.spec.ts

@@ -14,13 +14,11 @@ function mountBar(props: {
   likeCount: number;
   canDownload?: boolean;
   canDownloadOriginal?: boolean;
-  isLiking?: boolean;
 }): VueWrapper {
   const wrapper = mount(PhotoActionBar, {
     props: {
       canDownload: false,
       canDownloadOriginal: false,
-      isLiking: false,
       ...props,
     },
     global: { plugins: [i18n] },