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/pages/client/ClientNonUIFeatures.tsx

@@ -264,19 +264,20 @@ function MessageNotifications() {
 
 function QuickSwitcherFeature() {
   const [open, setOpen] = useState(false);
+  const [quickSwitcherKey] = useSetting(settingsAtom, 'quickSwitcherKey');
 
   useEffect(() => {
     const handleKeyDown = (e: KeyboardEvent) => {
-      if ((e.ctrlKey || e.metaKey) && e.key === 'p') {
+      if ((e.ctrlKey || e.metaKey) && e.code === quickSwitcherKey) {
         e.preventDefault();
-        setOpen(true);
+        setOpen((prev) => !prev);
       }
     };
     window.addEventListener('keydown', handleKeyDown);
     return () => {
       window.removeEventListener('keydown', handleKeyDown);
     };
-  }, []);
+  }, [quickSwitcherKey]);
 
   if (!open) return null;
   return <QuickSwitcher onClose={() => setOpen(false)} />;