fix: Add vertical slug prefix to song slugs for uniqueness

backend/importers/base.py

@@ -178,9 +178,11 @@ class ImporterBase(ABC):
         if existing:
             song_id = existing.id
         else:
+            # Include vertical slug in song slug for cross-band uniqueness
+            song_slug = f"{vertical.slug}-{generate_slug(title)}"
             song = Song(
                 title=title,
-                slug=generate_slug(title),
+                slug=song_slug,
                 original_artist=original_artist,
                 vertical_id=vertical.id
             )