domain: replace user-facing Jellyfin type badge with kind label (phase 3b)

The library detail page showed the raw Jellyfin item_type string
("MusicAlbum") to users. Add utils/mediaKind.ts with kindLabel(), a
presentation-only MediaKind -> human label map, and use it for the badge.
Flip the two remaining .type debug logs to .kind.

This removes the last user-visible Jellyfin vocabulary on the catalog
surface. primaryImageTag -> imageId rename (naming-only, ~40 sites across
catalog + player/merged types needing a Rust round-trip) intentionally
deferred as the lowest-value slice.

Frontend 644 tests, check clean.

src/lib/stores/library.ts

@@ -202,7 +202,7 @@ function createLibraryStore() {
       const repo = auth.getRepository();
       const item = await repo.getItem(itemId);
 
-      console.log(`[LibraryStore] loadItem(${itemId}): ${item.name} (${item.type})`);
+      console.log(`[LibraryStore] loadItem(${itemId}): ${item.name} (${item.kind})`);
       console.log(`[LibraryStore] - Has people? ${item.people ? `YES (${item.people.length})` : 'NO'}`);
       if (item.people && item.people.length > 0) {
         item.people.forEach((p, i) => {