feat(search): personalize suggestions by listening history (M6)

Suggest fetches three times as many candidates and reranks them in the API:
what the user plays, finishes and likes moves up a few positions and what they
dislike moves down, with Meilisearch relevance still the base order.

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

services/api/internal/search/service.go

@@ -28,12 +28,15 @@ type Handler struct {
 	meili   *Meili
 	catalog *library.Store
 	indexer *Indexer
+	aff     *Affinity
 	log     *slog.Logger
 }
 
 // NewHandler создаёт обработчик поиска.
-func NewHandler(meili *Meili, catalog *library.Store, indexer *Indexer, dto library.DTO, log *slog.Logger) *Handler {
-	return &Handler{meili: meili, catalog: catalog, indexer: indexer, dto: dto, log: log}
+func NewHandler(
+	meili *Meili, catalog *library.Store, indexer *Indexer, aff *Affinity, dto library.DTO, log *slog.Logger,
+) *Handler {
+	return &Handler{meili: meili, catalog: catalog, indexer: indexer, aff: aff, dto: dto, log: log}
 }
 
 type limits struct{ artists, albums, tracks, offset int }
@@ -150,10 +153,16 @@ func (h *Handler) hydrate(ctx context.Context, f found, corrected string) (gen.S
 
 // SearchSuggest реализует gen.StrictServerInterface.
 func (h *Handler) SearchSuggest(ctx context.Context, req gen.SearchSuggestRequestObject) (gen.SearchSuggestResponseObject, error) {
-	f, corrected, err := h.run(ctx, req.Params.Q, limits{artists: 3, albums: 3, tracks: 5})
+	want := limits{artists: 3, albums: 3, tracks: 5}
+	l := want
+	if h.aff != nil {
+		l = limits{artists: want.artists * suggestPool, albums: want.albums * suggestPool, tracks: want.tracks * suggestPool}
+	}
+	f, corrected, err := h.run(ctx, req.Params.Q, l)
 	if err != nil {
 		return nil, err
 	}
+	f = h.personal(ctx, f, want)
 	out, err := h.hydrate(ctx, f, corrected)
 	if err != nil {
 		return nil, err
@@ -161,6 +170,23 @@ func (h *Handler) SearchSuggest(ctx context.Context, req gen.SearchSuggestReques
 	return gen.SearchSuggest200JSONResponse(out), nil
 }
 
+// personal оставляет в подсказках по want.* лучших с учётом вкуса пользователя.
+// Без пользователя или при сбое — просто первые по релевантности.
+func (h *Handler) personal(ctx context.Context, f found, want limits) found {
+	var aff map[uuid.UUID]float64
+	if p, ok := auth.PrincipalFrom(ctx); ok && h.aff != nil {
+		all := ids(append(append(append([]string{}, f.artists...), f.albums...), f.tracks...))
+		var err error
+		if aff, err = h.aff.Of(ctx, p.UserID, all); err != nil {
+			h.log.WarnContext(ctx, "suggest personalization failed", "err", err)
+		}
+	}
+	f.artists = personalize(f.artists, aff, want.artists)
+	f.albums = personalize(f.albums, aff, want.albums)
+	f.tracks = personalize(f.tracks, aff, want.tracks)
+	return f
+}
+
 // Search реализует gen.StrictServerInterface.
 func (h *Handler) Search(ctx context.Context, req gen.SearchRequestObject) (gen.SearchResponseObject, error) {
 	typ := gen.All