fix(jellyfin): sort playlists by name (missing Playlist sort mapping)

applySort had no sortColumnsByType entry for the Playlist type, so
SortBy=SortName was ignored and the Playlists screen showed them in the
repo's default order. Map SortName/Name -> name (as Subsonic does) and
DateCreated -> created_at. Verified live: case-insensitive alphabetical.

server/jellyfin/e2e/playlists_test.go

@@ -94,6 +94,14 @@ var _ = Describe("Playlists", func() {
 			Expect(q.Items[0].Name).To(Equal("Listed"))
 			Expect(q.Items[0].ImageTags).To(HaveKey("Primary"))
 		})
+
+		It("sorts playlists by name when SortBy=SortName", func() {
+			createPlaylist("Charlie", nil)
+			createPlaylist("Alpha", nil)
+			createPlaylist("Bravo", nil)
+			q := queryResult(get("/Items?IncludeItemTypes=Playlist&Recursive=true&SortBy=SortName"))
+			Expect(names(q.Items)).To(Equal([]string{"Alpha", "Bravo", "Charlie"}))
+		})
 	})
 
 	Describe("cover art", func() {

server/jellyfin/items.go

@@ -457,6 +457,10 @@ var sortColumnsByType = map[string]map[string]string{
 	"MusicGenre": {
 		"sortname": "name", "name": "name",
 	},
+	"Playlist": {
+		"sortname": "name", "name": "name",
+		"datecreated": "created_at",
+	},
 }
 
 // sortColumn maps a single (non comma-list) Jellyfin SortBy key to the repo sort key for