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/state/settings.dart

@@ -0,0 +1,79 @@
+import 'package:flutter/foundation.dart';
+import 'package:hive_ce/hive.dart';
+import 'package:signals/signals_flutter.dart';
+
+// App preferences (Settings page), one Hive box. Signals start at their
+// defaults and take the stored values once [AppSettings.ensureLoaded]
+// finishes; setters write through.
+
+const settingsBoxName = 'settings';
+
+const _keyHwdecMode = 'hwdecMode';
+const _keyHwdecCustom = 'hwdecCustom';
+const _keyAutoCheckUpdates = 'autoCheckUpdates';
+
+enum HwdecMode { auto, off, custom }
+
+class AppSettings {
+  static final AppSettings instance = AppSettings();
+
+  final hwdecMode = signal(HwdecMode.auto);
+  final hwdecCustom = signal('');
+  final autoCheckUpdates = signal(true);
+
+  /// mpv `hwdec` value: 'auto', 'no', or the custom value ('auto' when
+  /// custom is blank).
+  late final hwdec = computed(() => switch (hwdecMode.value) {
+        HwdecMode.auto => 'auto',
+        HwdecMode.off => 'no',
+        HwdecMode.custom =>
+          hwdecCustom.value.trim().isEmpty ? 'auto' : hwdecCustom.value.trim(),
+      });
+
+  Future<void>? _load;
+  Box? _box;
+
+  Future<void> ensureLoaded() => _load ??= _loadNow();
+
+  Future<void> _loadNow() async {
+    try {
+      final box = _box = await Hive.openBox(settingsBoxName);
+      final mode = box.get(_keyHwdecMode);
+      hwdecMode.value = HwdecMode.values
+              .where((m) => m.name == mode)
+              .firstOrNull ??
+          HwdecMode.auto;
+      final custom = box.get(_keyHwdecCustom);
+      if (custom is String) hwdecCustom.value = custom;
+      final auto = box.get(_keyAutoCheckUpdates);
+      if (auto is bool) autoCheckUpdates.value = auto;
+    } catch (e, st) {
+      debugPrint('load settings failed: $e\n$st');
+    }
+  }
+
+  void setHwdecMode(HwdecMode mode) {
+    hwdecMode.value = mode;
+    _put(_keyHwdecMode, mode.name);
+  }
+
+  void setHwdecCustom(String value) {
+    hwdecCustom.value = value;
+    _put(_keyHwdecCustom, value);
+  }
+
+  void setAutoCheckUpdates(bool on) {
+    autoCheckUpdates.value = on;
+    _put(_keyAutoCheckUpdates, on);
+  }
+
+  Future<void> _put(String key, Object value) async {
+    try {
+      final box = _box ??
+          (Hive.isBoxOpen(settingsBoxName) ? Hive.box(settingsBoxName) : null);
+      await box?.put(key, value);
+    } catch (e, st) {
+      debugPrint('save setting $key failed: $e\n$st');
+    }
+  }
+}