vc=55: in-app auto-updater polling fdroid.sulkta.com

WorkManager periodic worker hits the repo's index-v2.json, parses
the highest versionCode for our package, compares with
BuildConfig.VERSION_CODE. When newer: posts a notification with
ACTION_VIEW on the APK URL — Android's DownloadManager picks it up
and the system installer takes over. No INSTALL_PACKAGES perm
needed.

Settings:
- Check for updates toggle (default on — closing NewPipe's silent
  staleness gap is the explicit motivation)
- Interval picker (1h / 6h / 24h, default 6h — WorkManager has a
  15-min periodic floor anyway)
- Last-checked timestamp + 'update available' tag when caught-up
  state is dirty
- Check now button — runs the same path as the worker so behaviors
  stay identical

Cold start fires one check too so users see pending updates without
waiting a full interval.

R8 keep-rule for UpdateCheckWorker added — WorkManager instantiates
workers by name via reflection.

strawApp/build.gradle.kts

@@ -130,6 +130,11 @@ dependencies {
     // Guava ListenableFuture support for awaiting MediaController connect.
     implementation("androidx.concurrent:concurrent-futures-ktx:1.2.0")
 
+    // WorkManager — periodic background poll of fdroid.sulkta.com index
+    // for self-update notifications. CoroutineWorker is built into the
+    // base work-runtime artifact as of 2.10.
+    implementation(libs.androidx.work.runtime)
+
     // strawcore — Rust YouTube extractor via UniFFI/JNA. Built by the
     // cargoBuild + uniffiBindgen tasks below; phase U-2+ exposes search /
     // streamInfo / channelInfo to replace NewPipeExtractor.