fix(album): bust public share images on cover edits; drop stale stamp copies

Share.CoverArtID built a bare Album{ID}, so public album-share image URLs
were a constant al-<id>_0 — combined with the 10-year cache header, viewers
kept the pre-edit cover forever. Use the loaded album when available so the
URL carries the real timestamps.

Also skip copying cover_art_updated_at in CopyAttributes when the source has
no uploaded_image (a cover removal leaves the stamp set), so an album-ID
merge can't overwrite the destination's valid cover stamp with a stale one.

model/share.go

@@ -37,6 +37,10 @@ func (s Share) CoverArtID() ArtworkID {
 	}
 	switch s.ResourceType {
 	case "album":
+		// Use the loaded album when available, so the public URL busts on cover edits
+		if len(s.Albums) > 0 && s.Albums[0].ID == ids[0] {
+			return s.Albums[0].CoverArtID()
+		}
 		return Album{ID: ids[0]}.CoverArtID()
 	case "playlist":
 		return Playlist{ID: ids[0]}.CoverArtID()

model/share_test.go

@@ -0,0 +1,24 @@
+package model_test
+
+import (
+	"time"
+
+	. "github.com/navidrome/navidrome/model"
+	. "github.com/onsi/ginkgo/v2"
+	. "github.com/onsi/gomega"
+)
+
+var _ = Describe("Share", func() {
+	Describe("CoverArtID", func() {
+		It("uses the loaded album, so the public URL busts on cover edits", func() {
+			s := Share{ResourceType: "album", ResourceIDs: "al-1"}
+			plain := s.CoverArtID().String()
+			Expect(s.CoverArtID().ID).To(Equal("al-1"))
+
+			stamp := time.Now()
+			s.Albums = Albums{{ID: "al-1", CoverArtUpdatedAt: &stamp}}
+			Expect(s.CoverArtID().ID).To(Equal("al-1"))
+			Expect(s.CoverArtID().String()).ToNot(Equal(plain))
+		})
+	})
+})

persistence/album_repository.go

@@ -299,10 +299,14 @@ func (r *albumRepository) CopyAttributes(fromID, toID string, columns ...string)
 		if col == "created_at" && (!v.Valid || v.String == "" || strings.HasPrefix(v.String, "0001-")) {
 			continue
 		}
-		// A source without an uploaded cover must not wipe one the destination has.
+		// A source without an uploaded cover must not wipe one the destination has,
+		// nor contribute a stale cover stamp left behind by a cover removal.
 		if (col == "uploaded_image" || col == "cover_art_updated_at") && (!v.Valid || v.String == "") {
 			continue
 		}
+		if col == "cover_art_updated_at" && (!from["uploaded_image"].Valid || from["uploaded_image"].String == "") {
+			continue
+		}
 		to[col] = v
 	}
 	if len(to) == 0 {

persistence/album_repository_test.go

@@ -174,6 +174,20 @@ var _ = Describe("AlbumRepository", func() {
 			Expect(got.UploadedImage).To(Equal("copy-dst_cover.jpg"))
 			Expect(got.CoverArtUpdatedAt).ToNot(BeNil())
 		})
+		It("does not copy a stale cover stamp left behind by a cover removal", func() {
+			// A removal clears uploaded_image but keeps cover_art_updated_at set
+			Expect(albumRepo.UpdateImage("copy-src", "copy-src_cover.jpg")).To(Succeed())
+			Expect(albumRepo.UpdateImage("copy-src", "")).To(Succeed())
+			Expect(albumRepo.UpdateImage("copy-dst", "copy-dst_cover.jpg")).To(Succeed())
+			before, err := albumRepo.Get("copy-dst")
+			Expect(err).ToNot(HaveOccurred())
+
+			Expect(albumRepo.CopyAttributes("copy-src", "copy-dst", "uploaded_image", "cover_art_updated_at")).To(Succeed())
+			got, err := albumRepo.Get("copy-dst")
+			Expect(err).ToNot(HaveOccurred())
+			Expect(got.UploadedImage).To(Equal("copy-dst_cover.jpg"))
+			Expect(got.CoverArtUpdatedAt.Equal(*before.CoverArtUpdatedAt)).To(BeTrue())
+		})
 	})
 
 	Describe("GetCursor", func() {