Desktop: video freeze recovery, session fixes, Home redesign

- Player + VideoController per session; Reload video (Ctrl+R) and a
  frozen-picture watchdog that reloads automatically.
- Shortcuts no longer fire while typing; empty swap disabled;
  hwdec setting/env actually applied.
- Idle unready measured from real inactivity; cancellable reconnects
  and setup; ready restored from server state; kicked/failed host
  stops its server; graceful leave on window close; no URLs with
  keys in display names.
- Welcome + connect screens replaced by one Home screen with Join and
  Host cards, recent servers, Settings, Integrations and About.

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

apps/desktop/lib/src/sync/room_diff.dart

@@ -39,6 +39,12 @@ bool localPlayAllowed(RoomBroadcast room, String memberId) {
   return false;
 }
 
+/// Self is ready but out of the set and fresh again: the server's stale
+/// sweep dropped it from the set during a signal gap and nothing puts it
+/// back. Re-sending ready restores it without the user pressing Space.
+bool shouldReassertReady(MemberView? self) =>
+    self != null && self.ready && !self.inSet && !self.stale;
+
 class RoomDiff {
   static const debounceWindow = Duration(seconds: 2);