feat: Android download page, analysis retry and a collapsible search

- /android is a public page with the latest APK, the server address to copy
  and three install steps; linked from the sign-in screen and the profile menu
- failed audio analysis can be retried from the library page, which also shows
  the most common error; the analyzer no longer burns attempts on files that
  are missing because the disk is not mounted
- the top bar search folds into a round button and slides open on click, "/"
  or Ctrl+K

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

services/api/internal/library/handler.go

@@ -292,6 +292,15 @@ func (h *Handler) ScanSource(ctx context.Context, req gen.ScanSourceRequestObjec
 	return gen.ScanSource202JSONResponse(progressDTO(p)), nil
 }
 
+// RetryAnalysis реализует gen.StrictServerInterface.
+func (h *Handler) RetryAnalysis(ctx context.Context, _ gen.RetryAnalysisRequestObject) (gen.RetryAnalysisResponseObject, error) {
+	n, err := h.svc.RetryAnalysis(ctx)
+	if err != nil {
+		return nil, err
+	}
+	return gen.RetryAnalysis200JSONResponse{Requeued: n}, nil
+}
+
 // GetLibraryStatus реализует gen.StrictServerInterface.
 func (h *Handler) GetLibraryStatus(ctx context.Context, _ gen.GetLibraryStatusRequestObject) (gen.GetLibraryStatusResponseObject, error) {
 	st, err := h.svc.Status(ctx)
@@ -304,7 +313,7 @@ func (h *Handler) GetLibraryStatus(ctx context.Context, _ gen.GetLibraryStatusRe
 		MissingFiles: int(c.Missing), FileErrors: int(c.Errors), Sources: []gen.SourceStatusItem{},
 		Analysis: gen.AnalysisStatus{
 			Queued: st.Analysis.Queued, Running: st.Analysis.Running, Done: st.Analysis.Done,
-			Failed: st.Analysis.Failed, AnalyzerVer: st.Analysis.AnalyzerVer,
+			Failed: st.Analysis.Failed, AnalyzerVer: st.Analysis.AnalyzerVer, TopError: st.Analysis.TopError,
 		},
 		Wave: gen.WaveMetrics{
 			Served: st.Wave.Served, Sessions: st.Wave.Sessions, ListenThroughRate: st.Wave.ListenThrough,

services/api/internal/library/service.go

@@ -587,6 +587,15 @@ func (s *Service) previewOne(ctx context.Context, root, rel string, patterns []m
 }
 
 // StartScan запускает скан источника в фоне.
+// RetryAnalysis возвращает в очередь треки, которые анализатор не смог обработать (например, пока диск
+// не был смонтирован).
+func (s *Service) RetryAnalysis(ctx context.Context) (int, error) {
+	if err := requirePerm(ctx, auth.PermManageLibrary); err != nil {
+		return 0, err
+	}
+	return s.store.RetryFailedAnalysis(ctx)
+}
+
 func (s *Service) StartScan(ctx context.Context, id uuid.UUID, full bool) (Progress, error) {
 	if err := requirePerm(ctx, auth.PermManageLibrary); err != nil {
 		return Progress{}, err

services/api/internal/library/store.go

@@ -605,7 +605,7 @@ func (st *Store) AlbumCoverPath(ctx context.Context, albumID uuid.UUID) (*string
 // AnalysisCounts — состояние очереди аудиоанализа.
 type AnalysisCounts struct {
 	Queued, Running, Done, Failed int
-	AnalyzerVer                   *string
+	AnalyzerVer, TopError         *string
 }
 
 // AnalysisCounts считает задачи анализа по статусам и текущую версию анализатора.
@@ -614,14 +614,27 @@ func (st *Store) AnalysisCounts(ctx context.Context) (AnalysisCounts, error) {
 	err := st.pool.QueryRow(ctx, `
 		SELECT count(*) FILTER (WHERE status = 'queued'), count(*) FILTER (WHERE status = 'running'),
 			count(*) FILTER (WHERE status = 'done'), count(*) FILTER (WHERE status = 'failed'),
-			(SELECT analyzer_ver FROM track_features ORDER BY analyzed_at DESC LIMIT 1)
-		FROM analysis_jobs`).Scan(&c.Queued, &c.Running, &c.Done, &c.Failed, &c.AnalyzerVer)
+			(SELECT analyzer_ver FROM track_features ORDER BY analyzed_at DESC LIMIT 1),
+			(SELECT error FROM analysis_jobs WHERE status = 'failed' AND error IS NOT NULL
+			 GROUP BY error ORDER BY count(*) DESC LIMIT 1)
+		FROM analysis_jobs`).Scan(&c.Queued, &c.Running, &c.Done, &c.Failed, &c.AnalyzerVer, &c.TopError)
 	if err != nil {
 		return AnalysisCounts{}, fmt.Errorf("library: analysis counts: %w", err)
 	}
 	return c, nil
 }
 
+// RetryFailedAnalysis возвращает неудавшиеся задачи анализа в очередь с нуля попыток.
+func (st *Store) RetryFailedAnalysis(ctx context.Context) (int, error) {
+	tag, err := st.pool.Exec(ctx, `
+		UPDATE analysis_jobs SET status = 'queued', attempts = 0, error = NULL, updated_at = now()
+		WHERE status = 'failed'`)
+	if err != nil {
+		return 0, fmt.Errorf("library: retry analysis: %w", err)
+	}
+	return int(tag.RowsAffected()), nil
+}
+
 // WaveMetrics — метрики волны за 7 дней (docs/recommendations.md#1-цели-и-как-измеряем-успех).
 type WaveMetrics struct {
 	Served, Sessions int