feat: 曲库索引 —— 曲库里已有的同名歌曲在列表中标记「曲库」

不是通过声匣下载的文件（其他工具 / 手动放入）以前一律显示未下载。
现在启动时扫描音乐目录，按「歌名 + 歌手文件夹 / 专辑文件夹」匹配，
下载完成增量更新，每 30 分钟或删除 / 补全标签后重建；设置页可手动重建。

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

web/src/components/TrackList.vue

@@ -35,7 +35,8 @@ watch(
 );
 
 const allSelected = computed(() => props.tracks.length > 0 && selected.value.size === props.tracks.length);
-const pendingCount = computed(() => props.tracks.filter((t) => !isDownloaded(t)).length);
+const owned = (t: TrackSummary) => isDownloaded(t) || !!t.inLibrary;
+const pendingCount = computed(() => props.tracks.filter((t) => !owned(t)).length);
 
 function toggleRow(index: number, e: MouseEvent) {
   const next = new Set(selected.value);
@@ -56,7 +57,7 @@ function toggleAll() {
 }
 
 function selectPending() {
-  selected.value = new Set(props.tracks.filter((t) => !isDownloaded(t)).map((t) => t.id));
+  selected.value = new Set(props.tracks.filter((t) => !owned(t)).map((t) => t.id));
 }
 
 async function downloadSelected() {
@@ -69,7 +70,14 @@ function downloadAll() {
   download(props.tracks, quality.value, props.group);
 }
 
-function rowState(t: TrackSummary) {
+interface RowState {
+  kind: string;
+  text: string;
+  pct: number;
+  title?: string;
+}
+
+function rowState(t: TrackSummary): RowState | null {
   const task = activeByTrack.value.get(trackKey(t.source, t.id));
   if (task) {
     if (task.status === 'running') {
@@ -80,6 +88,7 @@ function rowState(t: TrackSummary) {
     return { kind: task.status, text: task.status === 'paused' ? '已暂停' : '排队中', pct: 0 };
   }
   if (isDownloaded(t)) return { kind: 'done', text: '已下载', pct: 1 };
+  if (t.inLibrary) return { kind: 'library', text: '曲库中有', pct: 1, title: `曲库中有同名歌曲：${t.inLibrary}` };
   return null;
 }
 
@@ -158,9 +167,9 @@ const best = (t: TrackSummary) => bestQuality(t.qualities);
         </span>
         <span class="state">
           <template v-if="rowState(t)">
-            <span class="st" :class="rowState(t)!.kind">
-              <Icon v-if="rowState(t)!.kind === 'done'" name="check" :size="14" />
-              {{ rowState(t)!.kind === 'done' ? '' : rowState(t)!.text }}
+            <span class="st" :class="rowState(t)!.kind" :title="rowState(t)!.title ?? rowState(t)!.text">
+              <Icon v-if="rowState(t)!.kind === 'done' || rowState(t)!.kind === 'library'" name="check" :size="14" />
+              {{ rowState(t)!.kind === 'done' ? '' : rowState(t)!.kind === 'library' ? '曲库' : rowState(t)!.text }}
             </span>
             <span v-if="rowState(t)!.kind === 'running'" class="bar"><i :style="{ width: `${rowState(t)!.pct * 100}%` }" /></span>
           </template>
@@ -392,6 +401,11 @@ const best = (t: TrackSummary) => bestQuality(t.qualities);
   font-family: var(--font-mono);
 }
 
+.st.library {
+  color: var(--ink-3);
+  cursor: help;
+}
+
 .st.done {
   color: var(--ok);
 }

web/src/lib/api.ts

@@ -20,6 +20,8 @@ export interface TrackSummary {
   qualities?: QualityKey[];
   vip?: boolean;
   downloaded?: boolean;
+  /** 曲库中同名文件（相对路径），不是通过本服务下载的 */
+  inLibrary?: string;
 }
 
 export interface Paged<T> {
@@ -84,6 +86,7 @@ export interface TrackMeta {
   genre?: string;
   publisher?: string;
   downloaded?: boolean;
+  inLibrary?: string;
 }
 
 export interface QualityOption {
@@ -315,6 +318,8 @@ export const api = {
   libraryZipUrl: (path: string) => `/api/library/zip?${qs({ path })}`,
   writeM3u: (path: string) => request<{ file: string }>('/library/m3u', json('POST', { path })),
   trash: (path: string) => request<{ moved: string }>('/library/trash', json('POST', { path })),
+  libraryIndex: () => request<{ files: number; builtAt: string | null; building: boolean }>('/library/index'),
+  rebuildLibraryIndex: () => request<{ files: number; builtAt: string | null; building: boolean }>('/library/index', json('POST')),
   trashInfo: () => request<{ count: number; size: number }>('/library/trash'),
   emptyTrash: () => request('/library/trash', { method: 'DELETE' }),
   retagJob: () => request<{ job: RetagJob | null }>('/library/retag').then((r) => r.job),

web/src/views/SettingsView.vue

@@ -108,7 +108,18 @@ const themes: Array<{ key: ThemeMode; label: string }> = [
   { key: 'dark', label: '墨 · 深色' },
 ];
 
-onMounted(() => refreshAccounts());
+// ---- 曲库索引 ----
+const libIndex = ref<{ files: number; builtAt: string | null; building: boolean } | null>(null);
+async function reindex() {
+  libIndex.value = { ...(libIndex.value ?? { files: 0, builtAt: null }), building: true };
+  libIndex.value = await api.rebuildLibraryIndex().catch((e) => (toastError(e), null));
+  if (libIndex.value) toast(`曲库索引已重建：${libIndex.value.files} 个文件`, 'ok');
+}
+
+onMounted(() => {
+  refreshAccounts();
+  api.libraryIndex().then((i) => (libIndex.value = i)).catch(() => {});
+});
 </script>
 
 <template>
@@ -229,6 +240,11 @@ onMounted(() => refreshAccounts());
           {{ opt.label }}
         </label>
       </div>
+      <p v-if="libIndex" class="faint small index">
+        曲库索引：{{ libIndex.files }} 个音频文件<template v-if="libIndex.builtAt">，{{ relTime(libIndex.builtAt) }}更新</template>
+        —— 列表中「曲库」标记来自这里，每 30 分钟自动刷新
+        <button class="link" type="button" :disabled="libIndex.building" @click="reindex">{{ libIndex.building ? '重建中…' : '立即重建' }}</button>
+      </p>
       <p v-if="ffmpeg === false" class="warn small">未检测到 ffmpeg：FLAC 等非 MP3 文件无法写入标签。请安装 ffmpeg 并加入 PATH。</p>
     </section>
 
@@ -515,6 +531,10 @@ h3 {
   outline-offset: 2px;
 }
 
+.index {
+  margin: 16px 0 0;
+}
+
 .warn {
   color: var(--gold);
   margin: 14px 0 0;