feat: configurable keybindings for push-to-deafen and quick switcher

- Add deafenKey (default M) and quickSwitcherKey (default P) to settingsAtom
- Settings → Calls: Push to Deafen keybind tile using shared useKeyBind hook
- Settings → Keyboard Shortcuts: new section with Quick Room Switcher keybind
- Extract useKeyBind + keyLabel helpers to reduce duplication in Calls section
- CallControls reads deafenKey from settings (reactive, re-registers on change)
- ClientNonUIFeatures reads quickSwitcherKey from settings (same pattern)
- QuickSwitcher now toggles open/closed on repeat press (Ctrl+key again closes)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/app/state/settings.ts

@@ -80,6 +80,9 @@ export interface Settings {
 
   nightLightEnabled: boolean;
   nightLightOpacity: number;
+
+  deafenKey: string;
+  quickSwitcherKey: string;
 }
 
 const defaultSettings: Settings = {
@@ -129,6 +132,9 @@ const defaultSettings: Settings = {
 
   nightLightEnabled: false,
   nightLightOpacity: 30,
+
+  deafenKey: 'KeyM',
+  quickSwitcherKey: 'KeyP',
 };
 
 export const getSettings = (): Settings => {