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_compat.go

@@ -148,6 +148,9 @@ func (e *EmbyService) Items(ctx context.Context, p ItemsParams) (map[string]any,
 	if e.remote != nil {
 		// 远程目录浏览：ParentId 带远程前缀 → 完整转发给远程 Emby 承接分页。
 		if IsEmbyRemoteID(p.ParentID) {
+			if containsEmbyFilter(p.Filters, "IsFavorite") {
+				return e.favoriteItems(ctx, p)
+			}
 			mountID, _, _ := DecodeEmbyRemoteID(p.ParentID)
 			mount, acct, _ := e.remote.ResolveMount(ctx, mountID)
 			if mount == nil || acct == nil {
@@ -171,6 +174,9 @@ func (e *EmbyService) Items(ctx context.Context, p ItemsParams) (map[string]any,
 	if containsEmbyFilter(p.Filters, "IsResumable") {
 		return e.resumableItems(ctx, p)
 	}
+	if containsEmbyFilter(p.Filters, "IsFavorite") {
+		return e.favoriteItems(ctx, p)
+	}
 
 	if len(p.IDs) > 0 {
 		items := make([]map[string]any, 0, len(p.IDs))