style(android): rename package audio_cache -> audiocache

detekt's PackageNaming rule rejects underscores in package names
(Kotlin/Java convention is lowercase, no separator). Renamed
com.fabledsword.minstrel.cache.audio_cache -> .audiocache.

Pattern for future multi-word subpackages: smush rather than _
separator (e.g. mutationqueue, synccontroller, when those land).
The on-disk audio_cache/ dir path inside the app cache (PlayerFactory.kt:41)
is unaffected — that's a filename string, not a package.

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

android/app/src/main/java/com/fabledsword/minstrel/cache/audiocache/CacheConfig.kt

@@ -1,4 +1,4 @@
-package com.fabledsword.minstrel.cache.audio_cache
+package com.fabledsword.minstrel.cache.audiocache
 
 /**
  * Defaults for the 2-bucket audio cache. Matches the Flutter client.

android/app/src/main/java/com/fabledsword/minstrel/player/PlayerFactory.kt

@@ -11,7 +11,7 @@ import androidx.media3.datasource.cache.SimpleCache
 import androidx.media3.datasource.okhttp.OkHttpDataSource
 import androidx.media3.exoplayer.ExoPlayer
 import androidx.media3.exoplayer.source.DefaultMediaSourceFactory
-import com.fabledsword.minstrel.cache.audio_cache.CacheConfig
+import com.fabledsword.minstrel.cache.audiocache.CacheConfig
 import dagger.hilt.android.qualifiers.ApplicationContext
 import okhttp3.OkHttpClient
 import java.io.File

android/app/src/main/java/com/fabledsword/minstrel/player/PlayerModule.kt

@@ -1,6 +1,6 @@
 package com.fabledsword.minstrel.player
 
-import com.fabledsword.minstrel.cache.audio_cache.CacheConfig
+import com.fabledsword.minstrel.cache.audiocache.CacheConfig
 import dagger.Module
 import dagger.Provides
 import dagger.hilt.InstallIn