feat(viewer): UI-02 visual foundation, top bar and album info

V01+V02 (Task 2 of the UI-02 viewer redesign plan):

- viewer-tokens.css: UI-02 §3.1 design tokens scoped to .viewer-shell
  (never :root), so embed routes consume none of them
- App.vue: normal routes get a sticky white top bar (PhotoLive brand +
  compact locale switcher + lightweight "..." menu holding the
  reduce-motion toggle); global 16px content padding removed so banner
  and photos run edge-to-edge; embed shell branch untouched
- LocaleSwitcher: compact "EN/中文 + caret" trigger with a proper menu
  (current language checked), 44px touch target, Escape/outside close
- AlbumHeader (new): banner (2.4:1 mobile, 320px desktop cap,
  object-fit contain, collapses on missing/failed), 2-line expandable
  title + share button (clipboard copy with selectable-text fallback),
  3-line expandable pre-line description, meta row (Intl-formatted
  view count with em-dash fallback for unknown, album-timezone dates
  with full range on title, venue), Latest/Popular 44px tabs and
  category pills from the API with horizontal scroll + overflow fade
- ActivityPage: delegates the info area to AlbumHeader; sequence
  reset/sort-lock/category-by-id semantics unchanged; desktop content
  capped at 1120px
- i18n: viewer.* strings (brand/share/views/readMore/latest/popular/
  allCategories/noPhotos/newPhotos/reduceMotion/settings) in zh-CN+en
- tests: viewer-shell (token source + normal/embed isolation) and
  album-header (8 cases) specs; activity/i18n specs updated for the
  menu switcher and the em-dash unknown view count; e2e selectors
  refreshed

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

apps/viewer/src/i18n/locales/en.ts

@@ -63,6 +63,22 @@ export default {
     // 轮播中被移除（ws photo.hidden）的轻提示。
     photoRemoved: 'This photo has been removed',
     backToAlbum: 'Back to album',
+    // —— UI-02 (V01/V02) additions ——
+    brand: 'PhotoLive',
+    settings: 'Settings',
+    share: 'Share',
+    shareCopied: 'Link copied',
+    shareCopyFailed: 'Copy failed — please copy the link manually:',
+    views: '{count} views',
+    viewsUnknown: '—',
+    readMore: 'More',
+    readLess: 'Less',
+    latest: 'Latest',
+    popular: 'Popular',
+    allCategories: 'All',
+    noPhotos: 'Photos coming soon',
+    newPhotos: 'New photos',
+    reduceMotion: 'Reduce motion',
   },
   route: { tokenLabel: 'Album token', photoLabel: 'Photo' },
   errors: {

apps/viewer/src/i18n/locales/zh-CN.ts

@@ -63,6 +63,22 @@ export default {
     // PHOTO_NOT_PUBLIC 专用：不存在/未发布/已隐藏同码（防枚举），文案覆盖两种成因。
     photoUnavailable: '照片不存在或已下线',
     backToAlbum: '返回相册',
+    // —— UI-02（V01/V02）新增 ——
+    brand: 'PhotoLive',
+    settings: '设置',
+    share: '分享',
+    shareCopied: '链接已复制',
+    shareCopyFailed: '复制失败，请手动复制链接：',
+    views: '{count} 次浏览',
+    viewsUnknown: '—',
+    readMore: '展开',
+    readLess: '收起',
+    latest: '最新',
+    popular: '热门',
+    allCategories: '全部',
+    noPhotos: '照片即将上线',
+    newPhotos: '有新照片',
+    reduceMotion: '减少动画',
   },
   route: { tokenLabel: '相册令牌', photoLabel: '照片' },
   errors: {