fix(desktop): voice hotkeys are window-scoped unless Global is toggled

The old code registered every enabled hotkey through Electron globalShortcut
API, which captures system-wide. Setting M as mute meant m could not be
typed in any other app. Now the OS-level registration only happens when
binding.global === true; otherwise the existing window-keydown listener
handles it.

apps/desktop/src/context/CallContext.tsx

@@ -2004,14 +2004,16 @@ export function CallProvider({ children }: { children: ReactNode }) {
 
     const syncGlobalShortcuts = () => {
       if (!isTauriRuntime()) return;
+      // Only register an OS-level shortcut if the user explicitly opted in.
+      // Window-scoped firing happens via the `onKey` listener above and works
+      // for every enabled binding regardless of the `global` flag.
+      const enabledAndGlobal = (b: VoiceHotkeys[HotkeyKind]) => b.enabled && b.global;
       const desired: Record<HotkeyKind, string | null> = {
-        mute: settings.mute.enabled ? bindingToTauriShortcut(settings.mute) : null,
-        deafen: settings.deafen.enabled ? bindingToTauriShortcut(settings.deafen) : null,
-        hangup: settings.hangup.enabled ? bindingToTauriShortcut(settings.hangup) : null,
-        screenShare: settings.screenShare.enabled
-          ? bindingToTauriShortcut(settings.screenShare)
-          : null,
-        video: settings.video.enabled ? bindingToTauriShortcut(settings.video) : null,
+        mute:        enabledAndGlobal(settings.mute)        ? bindingToTauriShortcut(settings.mute)        : null,
+        deafen:      enabledAndGlobal(settings.deafen)      ? bindingToTauriShortcut(settings.deafen)      : null,
+        hangup:      enabledAndGlobal(settings.hangup)      ? bindingToTauriShortcut(settings.hangup)      : null,
+        screenShare: enabledAndGlobal(settings.screenShare) ? bindingToTauriShortcut(settings.screenShare) : null,
+        video:       enabledAndGlobal(settings.video)       ? bindingToTauriShortcut(settings.video)       : null,
       };
       for (const kind of KINDS) {
         const want = desired[kind];