Straw phases P/Q/R/S — bottom nav, sub feed, downloads, background audio

Phase P — bottom navigation:
- StrawHome restructured as a Scaffold with Material3 NavigationBar.
- Three tabs: Home (search + last 10 watches), Library (full watch
  history with count), Subs (channel chips + aggregated feed).

Phase Q — subscription feed:
- New SubscriptionFeedViewModel fans out per-channel ChannelInfo +
  ChannelTabs.VIDEOS fetches in parallel via async/awaitAll.
- Each channel contributes top 5; merged across all subs, capped at
  200, sorted by view count as a soft-recency proxy (extractor doesn't
  reliably surface upload timestamps).
- 10-minute cache TTL avoids hammering YT on tab re-entry.
- Subs tab renders the feed below the avatar row with a Refresh button.

Phase R — download:
- Download button on VideoDetail (next to Play / Share). Pops a tiny
  dialog: Audio (best audioStream) or Video (best videoStream/
  videoOnly fallback).
- Uses Android's DownloadManager — saves into app-private external
  files dir (Android/data/com.sulkta.straw.debug/files/Movies/<kind>/).
  Notification + progress for free. No WRITE_EXTERNAL_STORAGE needed.
- Filenames sanitized (no /:*?\"<>| chars), capped at 120 chars.

Phase S — background audio:
- New "Background" overlay button (🎧) on the player. Tap to pause the
  activity player and start PlaybackService with the audio URL.
- PlaybackService is a Media3 MediaSessionService with its own ExoPlayer
  configured with our custom DataSource.Factory (User-Agent set, cross-
  protocol redirects). Foreground service + media notification.
- Audio survives activity death — swipe the app out of recents, audio
  keeps playing. Stop via notification or open-the-app-and-tap-stop.
- onTaskRemoved keeps the service alive iff something is playing.

Versions shipped: P+Q as vc=4, R as vc=5, S as vc=6. Each landed in the
F-Droid repo for the day-by-day refresh path.

Day-N+ ideas: real MediaController unification (single Player for both
foreground + background paths), MergingMediaSource on the service side
for high-res YT videos, real upload-timestamp sort for feed once the
extractor exposes it consistently, queue/playlist.

buildSrc/src/main/kotlin/ProjectConfig.kt

@@ -15,6 +15,6 @@ const val NEWPIPE_APPLICATION_ID_OLD = "org.schabi.newpipe"
 const val NEWPIPE_APPLICATION_ID_NEW = "net.newpipe.app"
 
 // Sulkta fork — Straw
-const val STRAW_VERSION_CODE = 3
-const val STRAW_VERSION_NAME = "0.1.0-O"
+const val STRAW_VERSION_CODE = 6
+const val STRAW_VERSION_NAME = "0.1.0-S"
 const val STRAW_APPLICATION_ID = "com.sulkta.straw"