perf(android): decode posters at tile size, and keep disk reads off the main thread

- RemoteArtwork takes the edge it is drawn at; library tiles decode
  their posters at that size rather than at 1024 pixels, sampled down
  and then scaled so a poster never lands under its tile. The decoded
  cache's ceiling rises from 32 to 64 MiB, so a grid scrolled back over
  is still decoded.
- The title page decodes its download records on the IO dispatcher.
  WorkManager reports progress several times a second while a season
  downloads, and each report re-read every record on the main thread.
- The settings file is loaded on a background thread at startup, so the
  playback service's start callback no longer reads it from disk on the
  main thread (B41).

android/app/src/main/java/io/narl/protonstream/ProtonStreamApplication.kt

@@ -2,10 +2,15 @@ package io.narl.protonstream
 
 import android.app.Application
 import io.narl.protonstream.native.NativeRuntime
+import io.narl.protonstream.settings.SettingsStore
 
 class ProtonStreamApplication : Application() {
     override fun onCreate() {
         super.onCreate()
         NativeRuntime.initialize(this)
+        // SharedPreferences reads its file on first use, and the first use was
+        // on the main thread — in the playback service's start callback among
+        // others. Read here, off it, and every later read is from memory.
+        Thread({ SettingsStore.preload(this) }, "settings-preload").start()
     }
 }