feat(navidrome): Instant Mix probe, ping identity, and AudioMuse UX

Parse type and serverVersion from Subsonic ping; persist per-server identity and
run a background Instant Mix probe (random songs + getSimilarSongs) for
Navidrome 0.60+. Hide the AudioMuse server toggle when the probe returns no
similar tracks; clear prefs when the server is no longer eligible.

Artist pages fall back to Last.fm similar artists when AudioMuse is enabled but
the server returns none. Instant Mix failures set a per-server issue flag with a
settings warning and toast. Settings description links the official plugin repo
via i18n Trans.

src/locales/zh.ts

@@ -95,6 +95,7 @@ export const zhTranslation = {
     enqueueAlbum: '专辑加入队列',
     startRadio: '开始电台',
     instantMix: '即时混音',
+    instantMixFailed: '无法生成即时混音 — 服务器或插件出错。',
     lfmLove: '在 Last.fm 上标记喜欢',
     lfmUnlove: '取消 Last.fm 喜欢标记',
     favorite: '收藏',
@@ -395,7 +396,9 @@ export const zhTranslation = {
     serverCompatible: '兼容：Navidrome · Gonic · Airsonic · Subsonic',
     audiomuseTitle: 'AudioMuse-AI（Navidrome）',
     audiomuseDesc:
-      '若此服务器已配置 AudioMuse-AI Navidrome 插件请开启。可从曲目启动即时混音，并在艺人页使用服务器返回的相似艺人，而非 Last.fm。',
+      '若此服务器已配置 <pluginLink>AudioMuse-AI Navidrome 插件</pluginLink>请开启。可从曲目启动即时混音，并在艺人页使用服务器返回的相似艺人，而非 Last.fm。',
+    audiomuseIssueHint:
+      '近期即时混音失败 — 请检查 Navidrome 插件与 AudioMuse API。若服务器无结果，将回退使用 Last.fm 的相似艺人。',
     connected: '已连接',
     failed: '失败',
     eqTitle: '均衡器',