feat: mount VoiceOverlay and wire Space bar shortcut in App.vue

frontend/src/App.vue

@@ -3,6 +3,7 @@ import { onMounted, onUnmounted, ref, watch } from "vue";
 import { useRouter } from "vue-router";
 import AppHeader from "@/components/AppHeader.vue";
 import ToastNotification from "@/components/ToastNotification.vue";
+import VoiceOverlay from "@/components/VoiceOverlay.vue";
 import { useTheme } from "@/composables/useTheme";
 import { useShortcuts } from "@/composables/useShortcuts";
 import { useAuthStore } from "@/stores/auth";
@@ -120,6 +121,10 @@ function onGlobalKeydown(e: KeyboardEvent) {
         router.push("/chat");
       }
       break;
+    case " ":
+      e.preventDefault();
+      document.dispatchEvent(new CustomEvent("voice:ptt-toggle"));
+      break;
   }
 }
 
@@ -271,7 +276,7 @@ onUnmounted(() => {
               </div>
               <div class="shortcut-row">
                 <kbd class="shortcut-key">Space</kbd>
-                <span class="shortcut-desc">Hold to speak (voice, when enabled)</span>
+                <span class="shortcut-desc">Tap to speak (voice, when enabled)</span>
               </div>
             </div>
           </div>
@@ -282,6 +287,7 @@ onUnmounted(() => {
   <template v-else>
     <router-view />
   </template>
+  <VoiceOverlay />
   <ToastNotification />
 </template>