fix: sync mounted Emby favourites across web and Emby clients (#21)

Unify favourite writes through SyncUserFavorite so remote mounted media is
stored locally and proxied to the upstream Emby server. Emby clients now
query favourites from the local table (including remote pseudo IDs), and
remote item payloads merge local IsFavorite state.

Co-authored-by: Cursor Agent <cursoragent@cursor.com>
Co-authored-by: truewhile <truewhile@users.noreply.github.com>

internal/service/emby_items_detail.go

@@ -28,6 +28,14 @@ func (e *EmbyService) Item(ctx context.Context, mediaID, userID string) (map[str
 		if err := e.mergeRemoteUserData(ctx, userID, out); err != nil {
 			return nil, err
 		}
+		if favorite, _ := IsUserFavorite(ctx, e.repo, userID, mediaID); favorite {
+			userData, _ := out["UserData"].(map[string]any)
+			if userData == nil {
+				userData = map[string]any{}
+				out["UserData"] = userData
+			}
+			userData["IsFavorite"] = true
+		}
 		return out, nil
 	}
 	if lib, err := e.repo.Library.FindByID(ctx, mediaID); err != nil {
@@ -180,6 +188,137 @@ func (e *EmbyService) ResumeItems(ctx context.Context, userID string, limit int)
 	return e.resumableItems(ctx, ItemsParams{UserID: userID, Limit: limit})
 }
 
+// favoriteItems returns favourited media for Emby clients, including mounted
+// remote items stored only in the local favourites table.
+func (e *EmbyService) favoriteItems(ctx context.Context, p ItemsParams) (map[string]any, error) {
+	if p.Limit <= 0 || p.Limit > 500 {
+		p.Limit = 50
+	}
+	if p.StartIndex < 0 {
+		p.StartIndex = 0
+	}
+	if strings.TrimSpace(p.UserID) == "" {
+		return map[string]any{"Items": []any{}, "TotalRecordCount": int64(0), "StartIndex": p.StartIndex}, nil
+	}
+
+	var favs []model.Favorite
+	if err := e.repo.DB.WithContext(ctx).
+		Where("user_id = ?", p.UserID).
+		Order("created_at desc").
+		Find(&favs).Error; err != nil {
+		return nil, err
+	}
+	if len(favs) == 0 {
+		return map[string]any{"Items": []any{}, "TotalRecordCount": int64(0), "StartIndex": p.StartIndex}, nil
+	}
+
+	localIDs := make([]string, 0, len(favs))
+	for _, fav := range favs {
+		if !IsEmbyRemoteID(fav.MediaID) {
+			localIDs = append(localIDs, fav.MediaID)
+		}
+	}
+	byID := map[string]*model.Media{}
+	if len(localIDs) > 0 {
+		var medias []model.Media
+		q := e.repo.DB.WithContext(ctx).Where("id IN ?", localIDs)
+		q = e.applyUserMediaVisibility(ctx, q, p.UserID)
+		if err := q.Find(&medias).Error; err != nil {
+			return nil, err
+		}
+		for i := range medias {
+			byID[medias[i].ID] = &medias[i]
+		}
+	}
+
+	items := make([]map[string]any, 0, len(favs))
+	for _, fav := range favs {
+		if m, ok := byID[fav.MediaID]; ok {
+			if !favoriteMatchesParent(ctx, e, p.ParentID, fav.MediaID, m.LibraryID, m.SeriesID, nil) {
+				continue
+			}
+			if p.SearchTerm != "" {
+				needle := strings.ToLower(p.SearchTerm)
+				if !strings.Contains(strings.ToLower(m.Title), needle) &&
+					!strings.Contains(strings.ToLower(m.OriginalName), needle) {
+					continue
+				}
+			}
+			items = append(items, e.itemPayload(ctx, m, true, 0))
+			continue
+		}
+		if e.remote == nil || !IsEmbyRemoteID(fav.MediaID) {
+			continue
+		}
+		mountID, remoteID, _ := DecodeEmbyRemoteID(fav.MediaID)
+		mount, acct, err := e.remote.ResolveMount(ctx, mountID)
+		if err != nil || mount == nil || acct == nil {
+			continue
+		}
+		item, err := e.remote.RemoteItem(ctx, mount, acct, remoteID)
+		if err != nil || item == nil {
+			continue
+		}
+		if !favoriteMatchesParent(ctx, e, p.ParentID, fav.MediaID, "", "", item) {
+			continue
+		}
+		if p.SearchTerm != "" {
+			needle := strings.ToLower(p.SearchTerm)
+			name, _ := item["Name"].(string)
+			orig, _ := item["OriginalTitle"].(string)
+			if !strings.Contains(strings.ToLower(name), needle) &&
+				!strings.Contains(strings.ToLower(orig), needle) {
+				continue
+			}
+		}
+		userData, _ := item["UserData"].(map[string]any)
+		if userData == nil {
+			userData = map[string]any{}
+			item["UserData"] = userData
+		}
+		userData["IsFavorite"] = true
+		items = append(items, item)
+	}
+
+	total := int64(len(items))
+	if p.StartIndex >= len(items) {
+		return map[string]any{"Items": []map[string]any{}, "TotalRecordCount": total, "StartIndex": p.StartIndex}, nil
+	}
+	end := minInt(p.StartIndex+p.Limit, len(items))
+	return map[string]any{"Items": items[p.StartIndex:end], "TotalRecordCount": total, "StartIndex": p.StartIndex}, nil
+}
+
+func favoriteMatchesParent(ctx context.Context, e *EmbyService, parentID, mediaID, libraryID, seriesID string, remoteItem map[string]any) bool {
+	if parentID == "" {
+		return true
+	}
+	if libraryID != "" {
+		if libraryID == parentID || seriesID == parentID {
+			return true
+		}
+		for _, id := range e.mergedLibraryIDs(ctx, parentID) {
+			if id == libraryID {
+				return true
+			}
+		}
+		return false
+	}
+	if remoteItem == nil {
+		return false
+	}
+	itemParent, _ := remoteItem["ParentId"].(string)
+	itemSeries, _ := remoteItem["SeriesId"].(string)
+	if itemParent == parentID || itemSeries == parentID || mediaID == parentID {
+		return true
+	}
+	if !IsEmbyRemoteID(parentID) {
+		return false
+	}
+	wantMountID, _, _ := DecodeEmbyRemoteID(parentID)
+	gotMountID, _, _ := DecodeEmbyRemoteID(mediaID)
+	return wantMountID != "" && gotMountID == wantMountID
+}
+
 // resumableItems 返回未完成播放进度的媒体（包含本地媒体与挂载的远程媒体），支持分页。
 func (e *EmbyService) resumableItems(ctx context.Context, p ItemsParams) (map[string]any, error) {
 	if p.Limit <= 0 || p.Limit > 100 {