Add library favourite buttons and fix remote favourites list (#14)

* Add favourite buttons to library list and series detail pages

Co-authored-by: truewhile <truewhile@users.noreply.github.com>

* Fix favourites list for remote Emby mounted media

Co-authored-by: truewhile <truewhile@users.noreply.github.com>

* Route favourites to library series detail when appropriate

Co-authored-by: truewhile <truewhile@users.noreply.github.com>

* Fix favourites link to library series for remote anime paths

Co-authored-by: truewhile <truewhile@users.noreply.github.com>

---------

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

internal/service/playback_test.go

@@ -0,0 +1,46 @@
+package service
+
+import (
+	"context"
+	"testing"
+	"time"
+
+	"github.com/ShukeBta/MMTL/internal/model"
+	"github.com/ShukeBta/MMTL/internal/repository"
+	"go.uber.org/zap"
+)
+
+func TestListFavouritesIncludesLocalAndRemoteIDs(t *testing.T) {
+	db := newServiceTestDB(t, &model.Favorite{}, &model.Media{})
+	repos := repository.New(db)
+	userID := "user-1"
+	local := model.Media{
+		Base:  model.Base{ID: "local-movie-1"},
+		Title: "Local Movie",
+	}
+	if err := db.Create(&local).Error; err != nil {
+		t.Fatalf("create local media: %v", err)
+	}
+	remoteID := EncodeEmbyRemoteID("mount-1", "remote-series-1")
+	favs := []model.Favorite{
+		{Base: model.Base{CreatedAt: time.Now().Add(-time.Minute)}, UserID: userID, MediaID: remoteID},
+		{Base: model.Base{CreatedAt: time.Now()}, UserID: userID, MediaID: local.ID},
+	}
+	for i := range favs {
+		if err := db.Create(&favs[i]).Error; err != nil {
+			t.Fatalf("create favorite %d: %v", i, err)
+		}
+	}
+
+	svc := NewPlaybackService(zap.NewNop(), repos)
+	items, err := svc.ListFavourites(context.Background(), userID)
+	if err != nil {
+		t.Fatalf("ListFavourites: %v", err)
+	}
+	if len(items) != 1 {
+		t.Fatalf("expected one hydrated local favourite without remote service, got %d: %#v", len(items), items)
+	}
+	if items[0].ID != local.ID {
+		t.Fatalf("expected local favourite first by created_at desc, got %#v", items[0])
+	}
+}