Show album artist under album name on album cards (#2117)

## Description
Show album artist under album name on album cards

### Related issues
Fixes #2055

### Testing
Android TV 

## Screenshots
<img width="1920" height="1080" alt="pr1-albums-grid-artist-year"
src="https://github.com/user-attachments/assets/d00a8f78-8bf9-41da-8220-5cc7f6862cf5"
/>

### AI or LLM usage
Claude did the code, I reviewed it, then deployed a -debug.apk to my
device to confirm feature live.

Co-authored-by: Claude Sonnet 5.5 <noreply@anthropic.com>

app/src/test/java/com/github/damontecres/wholphin/data/model/BaseItemSubtitleTest.kt

@@ -0,0 +1,48 @@
+package com.github.damontecres.wholphin.data.model
+
+import org.jellyfin.sdk.model.api.BaseItemDto
+import org.jellyfin.sdk.model.api.BaseItemKind
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertNull
+import org.junit.Test
+import java.util.UUID
+
+class BaseItemSubtitleTest {
+    private fun album(
+        albumArtist: String? = null,
+        artists: List<String>? = null,
+        productionYear: Int? = null,
+    ) = BaseItem(
+        BaseItemDto(
+            id = UUID.randomUUID(),
+            type = BaseItemKind.MUSIC_ALBUM,
+            name = "Test Album",
+            albumArtist = albumArtist,
+            artists = artists,
+            productionYear = productionYear,
+        ),
+    )
+
+    @Test
+    fun albumPrefersAlbumArtist() {
+        val item = album(albumArtist = "Album Artist", artists = listOf("A", "B"), productionYear = 2021)
+        assertEquals("Album Artist - 2021", item.subtitle)
+    }
+
+    @Test
+    fun albumFallsBackToArtists() {
+        val item = album(artists = listOf("A", "B"), productionYear = 2021)
+        assertEquals("A, B - 2021", item.subtitle)
+    }
+
+    @Test
+    fun albumWithoutYear() {
+        assertEquals("Album Artist", album(albumArtist = "Album Artist").subtitle)
+    }
+
+    @Test
+    fun albumWithoutArtist() {
+        assertEquals("2021", album(productionYear = 2021).subtitle)
+        assertNull(album(artists = emptyList()).subtitle)
+    }
+}