feat(settings): clock format setting (Auto / 24h / 12h) (#742)

* feat(settings): clock format setting (Auto / 24h / 12h)

Reported on the Psysonic Discord — the Queue side panel's ETA label
and the sleep-timer preview both render via `formatClockTime`, which
just calls `toLocaleTimeString` and so follows the user's system
locale. On en-US that means AM/PM, with no in-app way out.

Add a tri-state **Clock Format** setting under
**Settings → System → App Behavior**:

* `auto` (default) — keep the existing locale-driven behaviour, so
  bestehende installs are unaffected on first launch.
* `24h` — force 24-hour wall-clock output everywhere
  `formatClockTime` is used.
* `12h` — force AM/PM output.

Wired through `authStore` (`clockFormat`, `setClockFormat`), exposed
via `CustomSelect` in `SystemTab`, and threaded into the two
consumers (`QueueHeader`, `PlaybackDelayModal`) so they re-render on
change. `formatClockTime` itself stays a pure helper — it accepts the
setting as an optional second argument and maps it to `hour12`.

Locale coverage: all nine bundled locales (en, de, es, fr, nl, nb,
ru, zh, ro) get the four new settings strings. Pin tests added for
the `setClockFormat` setter and the `hour12` mapping in
`formatClockTime`.

* docs(changelog): clock format setting + contributors (PR #742)

src/locales/zh/settings.ts

@@ -170,6 +170,11 @@ export const settings = {
   showTrayIconDesc: '在系统通知区域 / 菜单栏显示 Psysonic 图标。',
   minimizeToTray: '最小化到托盘',
   minimizeToTrayDesc: '关闭窗口时，Psysonic 将继续在系统托盘中运行，而不是退出。',
+  clockFormat: '时间格式',
+  clockFormatDesc: '队列预计结束时间和睡眠定时器预览使用的时间格式。',
+  clockFormatAuto: '自动（跟随系统）',
+  clockFormatTwentyFour: '24 小时制',
+  clockFormatTwelve: '12 小时制（AM/PM）',
   preloadMiniPlayer: '预加载迷你播放器',
   preloadMiniPlayerDesc: '在应用启动时于后台构建迷你播放器窗口，使其首次打开即可立即显示内容。会占用少量额外内存。',
   linuxWebkitSmoothScroll: '滚轮平滑（Linux）',