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/README.md

@@ -1,17 +1,5 @@
-# watch_together
+# apps/desktop
 
-A new Flutter project.
-
-## Getting Started
-
-This project is a starting point for a Flutter application.
-
-A few resources to get you started if this is your first Flutter project:
-
-- [Learn Flutter](https://docs.flutter.dev/get-started/learn-flutter)
-- [Write your first Flutter app](https://docs.flutter.dev/get-started/codelab)
-- [Flutter learning resources](https://docs.flutter.dev/reference/learning-resources)
-
-For help getting started with Flutter development, view the
-[online documentation](https://docs.flutter.dev/), which offers tutorials,
-samples, guidance on mobile development, and a full API reference.
+The Flutter desktop app (the only binary users run). Layout and rules:
+[../../docs/ARCHITECTURE.md](../../docs/ARCHITECTURE.md). Build and test:
+[../../docs/DEVELOPMENT.md](../../docs/DEVELOPMENT.md).