feat(android): port cached_artists / cached_albums / cached_tracks (M8 4.2 slice 1)

Mirrors flutter_client/lib/cache/db.dart's CachedArtists / CachedAlbums /
CachedTracks Drift tables. Library cache foundation — LibraryRepository
(Phase 5.2) reads cache-first through these DAOs and refreshes from
server via the sync controller (Phase 12.4).

Column names follow Kotlin idiom (camelCase) instead of Drift's
snake_case; the schema is internal to the native client and the wire
JSON conversion happens in feature-level mappers.

Each DAO carries:
  - observe* (Flow) for cache-first reads in ViewModels
  - getById/getByIds (suspend) for one-shot lookups
  - upsertAll (suspend, REPLACE) for sync writes
  - deleteByIds (suspend) for sync-driven deletes

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

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

@@ -3,7 +3,13 @@ package com.fabledsword.minstrel.cache.db
 import androidx.room.Database
 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.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.CachedTrackEntity
 import com.fabledsword.minstrel.cache.db.entities.SyncMetadataEntity
 
 /**
@@ -16,14 +22,15 @@ import com.fabledsword.minstrel.cache.db.entities.SyncMetadataEntity
  * change with explicit `Migration` entries; `fallbackToDestructiveMigration`
  * in `DatabaseModule` is the safety net while we're pre-v1.
  *
- * Most entity families land in Task 4.2 (one commit per Drift table
- * family). `SyncMetadataEntity` was pulled forward into Task 4.1 to
- * satisfy Room's "at least one entity required" compile-time check;
- * its consumer (SyncController) arrives in Phase 12.4.
+ * Entity families land in Task 4.2 slices. The set will grow until the
+ * whole Drift schema is mirrored.
  */
 @Database(
     entities = [
         SyncMetadataEntity::class,
+        CachedArtistEntity::class,
+        CachedAlbumEntity::class,
+        CachedTrackEntity::class,
     ],
     version = 1,
     exportSchema = true,
@@ -31,4 +38,7 @@ import com.fabledsword.minstrel.cache.db.entities.SyncMetadataEntity
 @TypeConverters(MinstrelTypeConverters::class)
 abstract class AppDatabase : RoomDatabase() {
     abstract fun syncMetadataDao(): SyncMetadataDao
+    abstract fun cachedArtistDao(): CachedArtistDao
+    abstract fun cachedAlbumDao(): CachedAlbumDao
+    abstract fun cachedTrackDao(): CachedTrackDao
 }

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

@@ -0,0 +1,29 @@
+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.CachedAlbumEntity
+import kotlinx.coroutines.flow.Flow
+
+@Dao
+interface CachedAlbumDao {
+    @Query("SELECT * FROM cached_albums ORDER BY sortTitle COLLATE NOCASE ASC")
+    fun observeAll(): Flow<List<CachedAlbumEntity>>
+
+    @Query(
+        "SELECT * FROM cached_albums " +
+            "WHERE artistId = :artistId ORDER BY sortTitle COLLATE NOCASE ASC",
+    )
+    fun observeByArtist(artistId: String): Flow<List<CachedAlbumEntity>>
+
+    @Query("SELECT * FROM cached_albums WHERE id = :id")
+    suspend fun getById(id: String): CachedAlbumEntity?
+
+    @Insert(onConflict = OnConflictStrategy.REPLACE)
+    suspend fun upsertAll(rows: List<CachedAlbumEntity>)
+
+    @Query("DELETE FROM cached_albums WHERE id IN (:ids)")
+    suspend fun deleteByIds(ids: List<String>)
+}

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

@@ -0,0 +1,23 @@
+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.CachedArtistEntity
+import kotlinx.coroutines.flow.Flow
+
+@Dao
+interface CachedArtistDao {
+    @Query("SELECT * FROM cached_artists ORDER BY sortName COLLATE NOCASE ASC")
+    fun observeAll(): Flow<List<CachedArtistEntity>>
+
+    @Query("SELECT * FROM cached_artists WHERE id = :id")
+    suspend fun getById(id: String): CachedArtistEntity?
+
+    @Insert(onConflict = OnConflictStrategy.REPLACE)
+    suspend fun upsertAll(rows: List<CachedArtistEntity>)
+
+    @Query("DELETE FROM cached_artists WHERE id IN (:ids)")
+    suspend fun deleteByIds(ids: List<String>)
+}

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

@@ -0,0 +1,29 @@
+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.CachedTrackEntity
+import kotlinx.coroutines.flow.Flow
+
+@Dao
+interface CachedTrackDao {
+    @Query(
+        "SELECT * FROM cached_tracks " +
+            "WHERE albumId = :albumId ORDER BY discNumber ASC, trackNumber ASC",
+    )
+    fun observeByAlbum(albumId: String): Flow<List<CachedTrackEntity>>
+
+    @Query("SELECT * FROM cached_tracks WHERE id = :id")
+    suspend fun getById(id: String): CachedTrackEntity?
+
+    @Query("SELECT * FROM cached_tracks WHERE id IN (:ids)")
+    suspend fun getByIds(ids: List<String>): List<CachedTrackEntity>
+
+    @Insert(onConflict = OnConflictStrategy.REPLACE)
+    suspend fun upsertAll(rows: List<CachedTrackEntity>)
+
+    @Query("DELETE FROM cached_tracks WHERE id IN (:ids)")
+    suspend fun deleteByIds(ids: List<String>)
+}

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

@@ -0,0 +1,22 @@
+package com.fabledsword.minstrel.cache.db.entities
+
+import androidx.room.Entity
+import androidx.room.PrimaryKey
+import kotlinx.datetime.Clock
+import kotlinx.datetime.Instant
+
+/**
+ * Cache row for one album. Mirrors `flutter_client/lib/cache/db.dart`'s
+ * `CachedAlbums` Drift table.
+ */
+@Entity(tableName = "cached_albums")
+data class CachedAlbumEntity(
+    @PrimaryKey val id: String,
+    val artistId: String,
+    val title: String,
+    val sortTitle: String,
+    val releaseDate: String? = null,
+    val coverPath: String? = null,
+    val mbid: String? = null,
+    val fetchedAt: Instant = Clock.System.now(),
+)

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

@@ -0,0 +1,26 @@
+package com.fabledsword.minstrel.cache.db.entities
+
+import androidx.room.Entity
+import androidx.room.PrimaryKey
+import kotlinx.datetime.Clock
+import kotlinx.datetime.Instant
+
+/**
+ * Cache row for one artist. Mirrors `flutter_client/lib/cache/db.dart`'s
+ * `CachedArtists` Drift table.
+ *
+ * Column names follow Kotlin idiom (camelCase) rather than Drift's
+ * snake_case — the schema is purely internal to the native client; the
+ * sync controller exchanges snake_case JSON with the server and our
+ * mappers translate at the boundary.
+ */
+@Entity(tableName = "cached_artists")
+data class CachedArtistEntity(
+    @PrimaryKey val id: String,
+    val name: String,
+    val sortName: String,
+    val mbid: String? = null,
+    val artistThumbPath: String? = null,
+    val artistFanartPath: String? = null,
+    val fetchedAt: Instant = Clock.System.now(),
+)

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

@@ -0,0 +1,25 @@
+package com.fabledsword.minstrel.cache.db.entities
+
+import androidx.room.Entity
+import androidx.room.PrimaryKey
+import kotlinx.datetime.Clock
+import kotlinx.datetime.Instant
+
+/**
+ * Cache row for one track. Mirrors `flutter_client/lib/cache/db.dart`'s
+ * `CachedTracks` Drift table.
+ */
+@Entity(tableName = "cached_tracks")
+data class CachedTrackEntity(
+    @PrimaryKey val id: String,
+    val albumId: String,
+    val artistId: String,
+    val title: String,
+    val durationMs: Int = 0,
+    val trackNumber: Int? = null,
+    val discNumber: Int? = null,
+    val filePath: String? = null,
+    val fileFormat: String? = null,
+    val genre: String? = null,
+    val fetchedAt: Instant = Clock.System.now(),
+)