fix(statistics): cache Subsonic stat fetches and localize duration units

Add 7-minute TTL caches (same idea as rating prefetch) for overview
album strips, random-song format sample, and paginated library
aggregates; key by server and music folder.

Introduce formatHumanHoursMinutes with common.duration* strings in all
locales for Statistics and playlist duration labels.

Refresh RU/ZH statistics and nav wording; fix zh playtime label.

src/api/subsonic.ts

@@ -425,6 +425,157 @@ export async function prefetchAlbumUserRatings(
   return out;
 }
 
+/** Paginated album stats for Statistics (playtime, counts, genre breakdown). Same TTL as rating prefetch. */
+export interface StatisticsLibraryAggregates {
+  playtimeSec: number;
+  albumsCounted: number;
+  songsCounted: number;
+  capped: boolean;
+  genres: SubsonicGenre[];
+}
+
+/** Key `prefix:serverId:folder` — Statistics caches share scope with `libraryFilterParams()`. */
+function statisticsPageCacheKey(prefix: string): string | null {
+  const { activeServerId, musicLibraryFilterByServer } = useAuthStore.getState();
+  if (!activeServerId) return null;
+  const folder = musicLibraryFilterByServer[activeServerId] ?? 'all';
+  const folderPart = folder === 'all' ? 'all' : folder;
+  return `${prefix}:${activeServerId}:${folderPart}`;
+}
+
+const statisticsAggregatesCache = new Map<string, { value: StatisticsLibraryAggregates; expiresAt: number }>();
+
+/**
+ * Walks up to 5000 newest albums (scoped by library filter). Cached per server + music folder for
+ * 7 minutes (same `RATING_CACHE_TTL` as album/artist rating prefetch).
+ * Unknown/missing album genre is stored as `value: ''`; UI should map to i18n.
+ */
+export async function fetchStatisticsLibraryAggregates(): Promise<StatisticsLibraryAggregates> {
+  const key = statisticsPageCacheKey('statsAgg');
+  if (key) {
+    const hit = statisticsAggregatesCache.get(key);
+    if (hit && Date.now() < hit.expiresAt) return hit.value;
+  }
+
+  let playtimeSec = 0;
+  let albumsCounted = 0;
+  let songsCounted = 0;
+  const genreAgg = new Map<string, { songCount: number; albumCount: number }>();
+  const pageSize = 500;
+  const maxPages = 10;
+  let capped = false;
+  let offset = 0;
+  let nextPage = getAlbumList('newest', pageSize, 0);
+  for (let page = 0; page < maxPages; page++) {
+    try {
+      const albums = await nextPage;
+      for (const a of albums) {
+        playtimeSec += a.duration ?? 0;
+        albumsCounted += 1;
+        const sc = a.songCount ?? 0;
+        songsCounted += sc;
+        const label = (a.genre?.trim()) ? a.genre.trim() : '';
+        let g = genreAgg.get(label);
+        if (!g) {
+          g = { songCount: 0, albumCount: 0 };
+          genreAgg.set(label, g);
+        }
+        g.songCount += sc;
+        g.albumCount += 1;
+      }
+      if (albums.length < pageSize) break;
+      if (page === maxPages - 1) {
+        capped = true;
+        break;
+      }
+      offset += pageSize;
+      nextPage = getAlbumList('newest', pageSize, offset);
+    } catch {
+      break;
+    }
+  }
+
+  const genres: SubsonicGenre[] = [...genreAgg.entries()]
+    .map(([value, c]) => ({ value, songCount: c.songCount, albumCount: c.albumCount }))
+    .sort((a, b) => b.songCount - a.songCount);
+
+  const result: StatisticsLibraryAggregates = {
+    playtimeSec,
+    albumsCounted,
+    songsCounted,
+    capped,
+    genres,
+  };
+  if (key) {
+    statisticsAggregatesCache.set(key, { value: result, expiresAt: Date.now() + RATING_CACHE_TTL });
+  }
+  return result;
+}
+
+/** Recent / frequent / highest album strips + artist count for Statistics. */
+export interface StatisticsOverviewData {
+  recent: SubsonicAlbum[];
+  frequent: SubsonicAlbum[];
+  highest: SubsonicAlbum[];
+  artistCount: number;
+}
+
+const statisticsOverviewCache = new Map<string, { value: StatisticsOverviewData; expiresAt: number }>();
+
+export async function fetchStatisticsOverview(): Promise<StatisticsOverviewData> {
+  const key = statisticsPageCacheKey('statsOverview');
+  if (key) {
+    const hit = statisticsOverviewCache.get(key);
+    if (hit && Date.now() < hit.expiresAt) return hit.value;
+  }
+  const [recent, frequent, highest, artists] = await Promise.all([
+    getAlbumList('recent', 20).catch(() => [] as SubsonicAlbum[]),
+    getAlbumList('frequent', 12).catch(() => [] as SubsonicAlbum[]),
+    getAlbumList('highest', 12).catch(() => [] as SubsonicAlbum[]),
+    getArtists().catch(() => [] as SubsonicArtist[]),
+  ]);
+  const result: StatisticsOverviewData = {
+    recent,
+    frequent,
+    highest,
+    artistCount: artists.length,
+  };
+  if (key) {
+    statisticsOverviewCache.set(key, { value: result, expiresAt: Date.now() + RATING_CACHE_TTL });
+  }
+  return result;
+}
+
+/** Format (suffix) histogram from a random sample for Statistics. */
+export interface StatisticsFormatSample {
+  rows: { format: string; count: number }[];
+  sampleSize: number;
+}
+
+const statisticsFormatCache = new Map<string, { value: StatisticsFormatSample; expiresAt: number }>();
+
+export async function fetchStatisticsFormatSample(): Promise<StatisticsFormatSample> {
+  const key = statisticsPageCacheKey('statsFormat');
+  if (key) {
+    const hit = statisticsFormatCache.get(key);
+    if (hit && Date.now() < hit.expiresAt) return hit.value;
+  }
+  const songs = await getRandomSongs(500).catch(() => [] as SubsonicSong[]);
+  const counts: Record<string, number> = {};
+  for (const song of songs) {
+    const fmt = song.suffix?.toUpperCase() ?? 'Unknown';
+    counts[fmt] = (counts[fmt] ?? 0) + 1;
+  }
+  const rows = Object.entries(counts)
+    .map(([format, count]) => ({ format, count }))
+    .sort((a, b) => b.count - a.count);
+  const result: StatisticsFormatSample = { rows, sampleSize: songs.length };
+  if (key) {
+    statisticsFormatCache.set(key, { value: result, expiresAt: Date.now() + RATING_CACHE_TTL });
+  }
+  return result;
+}
+
 export async function getArtists(): Promise<SubsonicArtist[]> {
   const data = await api<{ artists: { index: Array<{ artist: SubsonicArtist[] }> } }>('getArtists.view', {
     ...libraryFilterParams(),