Backport from the iOS version: offline downloads, home-first reconnect, stall warning, Close

- Downloads for offline listening: long-press a track, album, artist or
  playlist -> Download; Menu -> Downloads lists them (progress, space used/free,
  play/shuffle, retry, remove). Saved on the SD card (Android/data/com.minamp/
  files/downloads). MP3 originals kept as they are unless above a lower
  download quality; the rest transcoded to MP3 (320 kbps by default). One at a
  time, Range resume for originals, retried when the server is back, Wi-Fi lock.
- Downloaded tracks play from the SD card, offline too; plays made offline
  are reported to Plex when a connection works again.
- Server.pick: when last time's connection was remote, give the plain home
  addresses 2 s first (a hairpinned remote address kept us encrypted and
  capped at home). test/PreferHomeTest.java.
- Playback "playing" but not moving for 12 s: say so instead of staying silent.
- Menu -> Close Minamp: stop the music and close every screen.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tools/check_fit.py

@@ -88,6 +88,8 @@ def slots(D):
         ("pin status", ["pin_not_yet"], D["text_sub"], False, lambda W: W - 40 - 24, 3, ("12", "11")),
         ("pin instructions", ["pin_open"], D["text_sub"], False, lambda W: W - 40, 2, ()),
         ("queue title", ["up_next"], D["text_title"], True, lambda W: W - 3 * D["touch"] - 12, 1, ()),
+        ("downloads title (back + one action)", ["downloads"], D["text_title"], True, lambda W: W - 2 * D["touch"] - 12, 1, ()),
+        ("downloads empty", ["dl_empty"], D["text_status"], False, lambda W: W - 48, 5, ()),
         ("search hint", ["search_hint"], D["text_body"], False, lambda W: W - D["touch"] - 12 - 20, 1, ()),
         ("status message", ["queue_empty", "no_playlists", "pick_something", "nothing_playing"], D["text_status"], False,
          lambda W: W - 48, 2, ()),