fix(artwork): include top-level album folders in parent cover art lookup

The Path != "." guard added in #5451 was too aggressive — it excluded
any folder with Path=".", which includes top-level album folders (not
just the library root). Changed to ParentID != "" which correctly
excludes only the actual library root folder.

Fixes #5456

core/artwork/e2e/album_test.go

@@ -105,7 +105,7 @@ var _ = Describe("Album artwork resolution", func() {
 		// └── Album/
 		//     ├── disc1/
 		//     │   └── 01 - Track.mp3
-		//     └── cover.jpg            ← should win (parent-folder fallback, currently ignored — bug)
+		//     └── cover.jpg            ← should win (parent-folder fallback)
 		It("uses the parent-folder cover for single-disc-subfolder albums", func() {
 			conf.Server.CoverArtPriority = defaultCoverPriority
 			setLayout(fstest.MapFS{
@@ -119,6 +119,24 @@ var _ = Describe("Album artwork resolution", func() {
 		})
 	})
 
+	// Reproduces https://github.com/navidrome/navidrome/issues/5456
+	When("a top-level multi-disc album has cover.jpg at the album root and per-disc folder.jpg", func() {
+		It("prefers the album-root cover.jpg", func() {
+			conf.Server.CoverArtPriority = defaultCoverPriority
+			setLayout(fstest.MapFS{
+				"Album/CD1/01 - Track.mp3": trackFile(1, "Track CD1"),
+				"Album/CD2/01 - Track.mp3": trackFile(1, "Track CD2"),
+				"Album/cover.jpg":          imageFile("album-root"),
+				"Album/CD1/folder.jpg":     imageFile("disc1"),
+				"Album/CD2/folder.jpg":     imageFile("disc2"),
+			})
+			scan()
+
+			al := firstAlbum()
+			Expect(readArtwork(al.CoverArtID())).To(Equal(imageBytes("album-root")))
+		})
+	})
+
 	When("CoverArtPriority puts embedded first and the album has both embedded and external art", func() {
 		// Artist/
 		// └── Album/

core/artwork/e2e/disc_test.go

@@ -1,6 +1,7 @@
 package artworke2e_test
 
 import (
+	"fmt"
 	"testing/fstest"
 
 	"github.com/navidrome/navidrome/conf"
@@ -255,6 +256,45 @@ var _ = Describe("Disc artwork resolution", func() {
 		})
 	})
 
+	// Reproduces https://github.com/navidrome/navidrome/issues/5456
+	When("a top-level multi-disc album has cover.jpg and per-disc folder.jpg", func() {
+		// Album/                       (top-level, Path=".")
+		// ├── cover.jpg                ← album-level cover
+		// ├── Disc 01/
+		// │   ├── 01 - Track.mp3
+		// │   └── folder.jpg           ← disc 1 art
+		// ├── Disc 02/
+		// │   ├── 01 - Track.mp3
+		// │   └── folder.jpg
+		// └── Disc 03/
+		//     ├── 01 - Track.mp3
+		//     └── folder.jpg
+		It("uses album-root cover.jpg for album art and per-disc folder.jpg for each disc", func() {
+			conf.Server.DiscArtPriority = defaultDiscPriority
+			conf.Server.CoverArtPriority = defaultCoverPriority
+			layout := fstest.MapFS{
+				"Album/cover.jpg": imageFile("album-root-cover"),
+			}
+			for i := 1; i <= 3; i++ {
+				prefix := fmt.Sprintf("Album/Disc %02d/", i)
+				layout[prefix+"01 - Track.mp3"] = trackFile(1, fmt.Sprintf("T%d", i), map[string]any{"disc": fmt.Sprintf("%d", i)})
+				layout[prefix+"folder.jpg"] = imageFile(fmt.Sprintf("disc-%02d-folder", i))
+			}
+			setLayout(layout)
+			scan()
+
+			al := firstAlbum()
+
+			Expect(readArtwork(al.CoverArtID())).To(Equal(imageBytes("album-root-cover")))
+
+			for i := 1; i <= 3; i++ {
+				discID := model.NewArtworkID(model.KindDiscArtwork, model.DiscArtworkID(al.ID, i), &al.UpdatedAt)
+				Expect(readArtwork(discID)).To(Equal(imageBytes(fmt.Sprintf("disc-%02d-folder", i))),
+					"disc %d should use its own folder.jpg", i)
+			}
+		})
+	})
+
 	When("discsubtitle is set but no image filename matches the subtitle", func() {
 		// Artist/
 		// └── Album/

core/artwork/reader_album.go

@@ -131,7 +131,7 @@ func loadAlbumFoldersPaths(ctx context.Context, ds model.DataStore, albums ...mo
 			} else if err != nil {
 				return nil, nil, nil, err
 			}
-			if parentFolder != nil && parentFolder.Path != "." {
+			if parentFolder != nil && parentFolder.ParentID != "" {
 				folders = append(folders, *parentFolder)
 			}
 		}

core/artwork/reader_album_test.go

@@ -141,6 +141,7 @@ var _ = Describe("Album Artwork Reader", func() {
 				ID:              "parentFolder",
 				Path:            "Artist",
 				Name:            "Album",
+				ParentID:        "artistFolder",
 				ImagesUpdatedAt: expectedAt,
 				ImageFiles:      []string{"cover.jpg", "back.jpg"},
 			}
@@ -213,14 +214,14 @@ var _ = Describe("Album Artwork Reader", func() {
 			Expect(repo.getCallCount).To(Equal(0))
 		})
 
-		It("does not include top-level parent for multi-folder albums", func() {
-			// Two album parts under the same artist folder — parent is artist-level
+		It("does not include library root parent for multi-folder albums", func() {
+			// Two album parts directly under the library root — parent is the root itself
 			repo.result = []model.Folder{
 				{
 					ID:              "folder1",
 					Path:            ".",
 					Name:            "AlbumPart1",
-					ParentID:        "artistFolder",
+					ParentID:        "rootFolder",
 					ImagesUpdatedAt: now,
 					ImageFiles:      []string{"cover.jpg"},
 				},
@@ -228,16 +229,17 @@ var _ = Describe("Album Artwork Reader", func() {
 					ID:              "folder2",
 					Path:            ".",
 					Name:            "AlbumPart2",
-					ParentID:        "artistFolder",
+					ParentID:        "rootFolder",
 					ImagesUpdatedAt: now,
 					ImageFiles:      []string{},
 				},
 			}
 			repo.parentResult = &model.Folder{
-				ID:         "artistFolder",
-				Path:       ".",
-				Name:       "Artist",
-				ImageFiles: []string{"artist.jpg"},
+				ID:         "rootFolder",
+				Path:       "",
+				Name:       ".",
+				ParentID:   "",
+				ImageFiles: []string{"unrelated.jpg"},
 			}
 
 			_, imgFiles, _, err := loadAlbumFoldersPaths(ctx, ds, album)
@@ -248,6 +250,46 @@ var _ = Describe("Album Artwork Reader", func() {
 			Expect(repo.getCallCount).To(Equal(1))
 		})
 
+		It("includes top-level album folder for multi-disc albums", func() {
+			// Album folder directly under artist root, with disc subfolders
+			repo.result = []model.Folder{
+				{
+					ID:              "folder1",
+					Path:            "Album",
+					Name:            "Disc1",
+					ParentID:        "albumFolder",
+					ImagesUpdatedAt: now,
+					ImageFiles:      []string{"folder.jpg"},
+				},
+				{
+					ID:              "folder2",
+					Path:            "Album",
+					Name:            "Disc2",
+					ParentID:        "albumFolder",
+					ImagesUpdatedAt: now,
+					ImageFiles:      []string{"folder.jpg"},
+				},
+			}
+			repo.parentResult = &model.Folder{
+				ID:              "albumFolder",
+				Path:            ".",
+				Name:            "Album",
+				ParentID:        "rootFolder",
+				ImagesUpdatedAt: expectedAt,
+				ImageFiles:      []string{"cover.jpg"},
+			}
+
+			_, imgFiles, imagesUpdatedAt, err := loadAlbumFoldersPaths(ctx, ds, album)
+
+			Expect(err).ToNot(HaveOccurred())
+			Expect(*imagesUpdatedAt).To(Equal(expectedAt))
+			Expect(imgFiles).To(HaveLen(3))
+			Expect(imgFiles[0]).To(Equal("Album/cover.jpg"))
+			Expect(imgFiles[1]).To(Equal("Album/Disc1/folder.jpg"))
+			Expect(imgFiles[2]).To(Equal("Album/Disc2/folder.jpg"))
+			Expect(repo.getCallCount).To(Equal(1))
+		})
+
 		It("does not query parent for single-folder albums that already have images", func() {
 			repo.result = []model.Folder{
 				{
@@ -283,6 +325,7 @@ var _ = Describe("Album Artwork Reader", func() {
 				ID:              "albumFolder",
 				Path:            "Artist",
 				Name:            "Album",
+				ParentID:        "artistFolder",
 				ImagesUpdatedAt: expectedAt,
 				ImageFiles:      []string{"cover.jpg"},
 			}