feat(android): port cached_likes (M8 4.2 slice 2)

Mirrors flutter_client/lib/cache/db.dart's CachedLikes Drift table —
composite PK (userId, entityType, entityId) so the same user can
like a track and its album and its artist independently. entityType
is a plain string ("track" | "album" | "artist") for parity with the
Drift schema and the server wire format.

DAO surface tailored to consumers we know are coming:
  - observeLikedTrackIds(userId): Flow<List<String>> — audio-cache
    eviction reads this set to identify "liked" bucket members
  - observeLikedIdsOfType(userId, entityType): generalized variant
  - observeIsLiked(...): scalar Flow for LikeButton composables
  - upsertAll (sync writes)
  - delete (mutation queue → toggle off)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

android/app/src/main/java/com/fabledsword/minstrel/cache/db/AppDatabase.kt

@@ -5,10 +5,12 @@ import androidx.room.RoomDatabase
 import androidx.room.TypeConverters
 import com.fabledsword.minstrel.cache.db.dao.CachedAlbumDao
 import com.fabledsword.minstrel.cache.db.dao.CachedArtistDao
+import com.fabledsword.minstrel.cache.db.dao.CachedLikeDao
 import com.fabledsword.minstrel.cache.db.dao.CachedTrackDao
 import com.fabledsword.minstrel.cache.db.dao.SyncMetadataDao
 import com.fabledsword.minstrel.cache.db.entities.CachedAlbumEntity
 import com.fabledsword.minstrel.cache.db.entities.CachedArtistEntity
+import com.fabledsword.minstrel.cache.db.entities.CachedLikeEntity
 import com.fabledsword.minstrel.cache.db.entities.CachedTrackEntity
 import com.fabledsword.minstrel.cache.db.entities.SyncMetadataEntity
 
@@ -31,6 +33,7 @@ import com.fabledsword.minstrel.cache.db.entities.SyncMetadataEntity
         CachedArtistEntity::class,
         CachedAlbumEntity::class,
         CachedTrackEntity::class,
+        CachedLikeEntity::class,
     ],
     version = 1,
     exportSchema = true,
@@ -41,4 +44,5 @@ abstract class AppDatabase : RoomDatabase() {
     abstract fun cachedArtistDao(): CachedArtistDao
     abstract fun cachedAlbumDao(): CachedAlbumDao
     abstract fun cachedTrackDao(): CachedTrackDao
+    abstract fun cachedLikeDao(): CachedLikeDao
 }

android/app/src/main/java/com/fabledsword/minstrel/cache/db/dao/CachedLikeDao.kt

@@ -0,0 +1,39 @@
+package com.fabledsword.minstrel.cache.db.dao
+
+import androidx.room.Dao
+import androidx.room.Insert
+import androidx.room.OnConflictStrategy
+import androidx.room.Query
+import com.fabledsword.minstrel.cache.db.entities.CachedLikeEntity
+import kotlinx.coroutines.flow.Flow
+
+@Dao
+interface CachedLikeDao {
+    /** All track IDs the user has liked. Audio-cache eviction uses this set. */
+    @Query(
+        "SELECT entityId FROM cached_likes " +
+            "WHERE userId = :userId AND entityType = 'track'",
+    )
+    fun observeLikedTrackIds(userId: String): Flow<List<String>>
+
+    @Query(
+        "SELECT entityId FROM cached_likes " +
+            "WHERE userId = :userId AND entityType = :entityType",
+    )
+    fun observeLikedIdsOfType(userId: String, entityType: String): Flow<List<String>>
+
+    @Query(
+        "SELECT EXISTS(SELECT 1 FROM cached_likes " +
+            "WHERE userId = :userId AND entityType = :entityType AND entityId = :entityId)",
+    )
+    fun observeIsLiked(userId: String, entityType: String, entityId: String): Flow<Boolean>
+
+    @Insert(onConflict = OnConflictStrategy.REPLACE)
+    suspend fun upsertAll(rows: List<CachedLikeEntity>)
+
+    @Query(
+        "DELETE FROM cached_likes " +
+            "WHERE userId = :userId AND entityType = :entityType AND entityId = :entityId",
+    )
+    suspend fun delete(userId: String, entityType: String, entityId: String)
+}

android/app/src/main/java/com/fabledsword/minstrel/cache/db/entities/CachedLikeEntity.kt

@@ -0,0 +1,26 @@
+package com.fabledsword.minstrel.cache.db.entities
+
+import androidx.room.Entity
+import kotlinx.datetime.Clock
+import kotlinx.datetime.Instant
+
+/**
+ * Like membership row. Mirrors `flutter_client/lib/cache/db.dart`'s
+ * `CachedLikes` Drift table. Composite primary key — one user may
+ * independently like a track AND its album AND its artist; rows are
+ * disambiguated by the (userId, entityType, entityId) triple.
+ *
+ * `entityType` is one of "track" | "album" | "artist". Stored as a
+ * plain string for parity with the Drift schema and the server's wire
+ * format; an enum doesn't earn its keep here.
+ */
+@Entity(
+    tableName = "cached_likes",
+    primaryKeys = ["userId", "entityType", "entityId"],
+)
+data class CachedLikeEntity(
+    val userId: String,
+    val entityType: String,
+    val entityId: String,
+    val likedAt: Instant = Clock.System.now(),
+)