feat(settings): results-only search, keyboard nav, flash animation, Ctrl+F (#264)

Follow-up on #263. Refines the cross-tab search into a proper
command-palette-ish flow and polishes the UX around it.

Results-only mode:
- When a query is active, the tab content is hidden entirely; the
  results list is the only thing shown. Unified list (was: in-place
  current-tab filter + "In other tabs" panel underneath), sorted with
  current-tab matches first and then by score.
- Removed the DOM-based hide/show logic and its CSS helper class, the
  dead searchOtherTabs i18n key, and the searchHits/otherTabHits state.

Keyboard navigation inside the search field:
- ↓/↑ moves selection through the result list (clamped, no wrap).
- Enter activates the selected item (same flow as a click — clears
  query, switches tab, scrolls + opens + flashes the target).
- Mouse hover syncs with the keyboard selection so the two input modes
  don't fight each other.
- Selected item gets accent-border + tinted background; scrollIntoView
  with block:'nearest' keeps it visible when the list is long.

Ctrl/Cmd+F (Settings page only):
- Window keydown listener registered on mount, removed on unmount →
  the shortcut is live only while Settings is rendered.
- Opens the search input, focuses + selects it even if already open.
- preventDefault blocks the native WebKit find bar.
- Placeholder now hints at the shortcut: "… (Ctrl+F)" / "… (⌘F)" on
  macOS, no new i18n keys needed.

Target flash animation:
- After navigating from a result, the target SettingsSubSection gets a
  1.4s accent-colored border + glow pulse so the user immediately sees
  which entry the result pointed at. Reflow trick lets it retrigger
  when clicking the same result twice.

Misc:
- "Next Track Buffering" → "Buffering" in all 8 locales + the section
  comment in Settings.tsx. The SETTINGS_INDEX keeps "next track" as a
  keyword so old search habits still find it.

Co-authored-by: Psychotoxical <dev@psysonic.app>
Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/locales/zh.ts

@@ -689,7 +689,6 @@ export const zhTranslation = {
     aboutContributorsCount_other: '{{count}} 项贡献',
     searchPlaceholder: '搜索设置…',
     searchNoResults: '没有设置匹配您的搜索。',
-    searchOtherTabs: '在其他标签页中',
     aboutMaintainersLabel: '维护者',
     integrationsPrivacyTitle: '隐私说明',
     integrationsPrivacyBody: '此标签页中的所有集成均为 <strong>选择加入</strong>，启用后会向外部服务或您的 Navidrome 服务器发送数据。Last.fm 接收您的收听历史，Discord 在您的个人资料中显示正在播放的曲目，Bandsintown 会按艺人查询以获取巡演日期，"正在播放" 分享会向您 Navidrome 服务器的其他用户公开您当前的曲目。如果您不需要这些功能，只需将相应部分保持停用即可。',
@@ -777,7 +776,7 @@ export const zhTranslation = {
     gaplessDesc: '预缓冲下一首曲目以消除歌曲间的间隙',
     preloadMode: '预加载下一曲目',
     preloadModeDesc: '何时开始缓冲队列中的下一曲目',
-    nextTrackBufferingTitle: '下一曲目缓冲',
+    nextTrackBufferingTitle: '缓冲',
     preloadHotCacheMutualExclusive: '预加载与热缓存用途相同——两者不能同时启用。启用其中一个会自动禁用另一个。',
     preloadOff: '关闭',
     preloadBalanced: '均衡（结束前30秒）',