fix(persistence): keep the new item's annotation when reassigning onto an item the user already annotated

ReassignAnnotation was a plain UPDATE; the annotation table is unique on
(user_id, item_id, item_type), so when a user had annotated both items the
statement aborted and none of the rows moved. In the scanner that surfaced as
a warning; in the missing-file remap it rolled back the whole operation.
UPDATE OR IGNORE moves what it can and leaves the conflicting rows for GC.

persistence/sql_annotations.go

@@ -185,10 +185,9 @@ func (r sqlRepository) ReassignAnnotation(prevID string, newID string) error {
 	if prevID == newID || prevID == "" || newID == "" {
 		return nil
 	}
-	upd := Update(annotationTable).Where(And{
-		Eq{annotationTable + ".item_type": r.tableName},
-		Eq{annotationTable + ".item_id": prevID},
-	}).Set("item_id", newID)
+	// OR IGNORE keeps newID's own row where a user annotated both, instead of aborting the whole statement
+	upd := Expr("update or ignore "+annotationTable+" set item_id = ? where item_type = ? and item_id = ?",
+		newID, r.tableName, prevID)
 	_, err := r.executeSQL(upd)
 	return err
 }

persistence/sql_annotations_test.go

@@ -30,6 +30,43 @@ var _ = Describe("Annotation Filters", func() {
 		_, _ = albumRepo.executeSQL(squirrel.Delete("album").Where(squirrel.Eq{"id": albumWithoutAnnotation.ID}))
 	})
 
+	Describe("ReassignAnnotation", func() {
+		var prev, next model.Album
+
+		BeforeEach(func() {
+			prev = model.Album{ID: "reassign-prev", Name: "Prev", LibraryID: 1}
+			next = model.Album{ID: "reassign-next", Name: "Next", LibraryID: 1}
+			Expect(albumRepo.Put(&prev)).To(Succeed())
+			Expect(albumRepo.Put(&next)).To(Succeed())
+		})
+
+		AfterEach(func() {
+			_, _ = albumRepo.executeSQL(squirrel.Delete("annotation").Where(squirrel.Eq{"item_id": []string{prev.ID, next.ID}}))
+			_, _ = albumRepo.executeSQL(squirrel.Delete("album").Where(squirrel.Eq{"id": []string{prev.ID, next.ID}}))
+		})
+
+		It("moves the annotation when the new item has none", func() {
+			Expect(albumRepo.SetRating(4, prev.ID)).To(Succeed())
+
+			Expect(albumRepo.ReassignAnnotation(prev.ID, next.ID)).To(Succeed())
+
+			got, err := albumRepo.Get(next.ID)
+			Expect(err).ToNot(HaveOccurred())
+			Expect(got.Rating).To(Equal(4))
+		})
+
+		It("keeps the new item's annotation when both exist", func() {
+			Expect(albumRepo.SetRating(4, prev.ID)).To(Succeed())
+			Expect(albumRepo.SetRating(2, next.ID)).To(Succeed())
+
+			Expect(albumRepo.ReassignAnnotation(prev.ID, next.ID)).To(Succeed())
+
+			got, err := albumRepo.Get(next.ID)
+			Expect(err).ToNot(HaveOccurred())
+			Expect(got.Rating).To(Equal(2))
+		})
+	})
+
 	Describe("annotationBoolFilter", func() {
 		DescribeTable("creates correct SQL expressions",
 			func(field, value string, expectedSQL string, expectedArgs []any) {