feat(mobile): keep voice alive with the screen off

A call dropped as soon as the screen locked. The cause is not configuration:
Android freezes background processes, and a frozen WebView stops running the
JavaScript that holds the LiveKit connection up. The only thing the system
accepts as "this app must keep running" is a foreground service, which is why
the persistent notification comes with it.

Two mechanisms, both needed: the service stops the process from being frozen,
and a partial wake lock stops the CPU from sleeping. Either one alone still
drops the call.

The notification carries a hangup action. The service cannot end the call
itself — only the web app knows how to leave a LiveKit room — so it notifies
the plugin's listeners and the web side disconnects through the same path the
in-app button uses.

The web side starts the service on mount when a call is already in progress,
not just on transition: the WebView can reload mid-call, and waiting for the
next connect would leave that call unprotected with no visible symptom until
someone locked their screen.

POST_NOTIFICATIONS is requested at launch on Android 13+. Denying it does not
drop calls — the service still runs — it only hides the notification.

Tests cover connect/disconnect, the already-in-a-call mount, the hangup action,
and that the component is inert in the browser and desktop builds. Verified by
mutation that dropping the start call fails the first one.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

packages/web/src/components/voice/AndroidVoiceService.tsx

@@ -0,0 +1,69 @@
+import { useEffect, useRef } from 'react';
+
+import { useVoiceStore } from '../../stores/voiceStore';
+import { useSpaceStore } from '../../stores/spaceStore';
+import {
+  isAndroidApp,
+  onAndroidHangup,
+  startAndroidVoiceService,
+  stopAndroidVoiceService,
+} from '../../platform/androidVoice';
+
+/**
+ * Liga e desliga o servico de primeiro plano do Android conforme a chamada
+ * comeca e termina. Nao renderiza nada; fora do APK nao faz nada.
+ *
+ * Assina a store direto, sem seletor de re-render: o efeito colateral e uma
+ * chamada ao nativo, e uma re-renderizacao por mudanca de estado da voz seria
+ * so custo.
+ */
+export function AndroidVoiceService() {
+  const wasConnected = useRef(useVoiceStore.getState().isLiveKitConnected);
+
+  useEffect(() => {
+    if (!isAndroidApp()) return;
+
+    const channelLabel = (channelId: string | null): string | undefined => {
+      if (!channelId) return undefined;
+      if (channelId.startsWith('dm-')) return 'Chamada';
+      return useSpaceStore.getState().channels.find((c) => c.id === channelId)?.name;
+    };
+
+    // Entrar na call e o gatilho, mas a montagem pode acontecer com uma
+    // chamada ja em andamento — uma recarga da WebView, por exemplo. Nesse caso
+    // o servico precisa subir agora, nao na proxima transicao.
+    const initial = useVoiceStore.getState();
+    if (initial.isLiveKitConnected) {
+      startAndroidVoiceService(channelLabel(initial.currentVoiceChannelId));
+    }
+
+    const unsubscribe = useVoiceStore.subscribe((state) => {
+      const connected = state.isLiveKitConnected;
+      if (connected === wasConnected.current) return;
+      wasConnected.current = connected;
+
+      if (connected) startAndroidVoiceService(channelLabel(state.currentVoiceChannelId));
+      else stopAndroidVoiceService();
+    });
+
+    const removeHangup = onAndroidHangup(() => {
+      // A notificacao so pede para sair; quem sabe encerrar a sessao do LiveKit
+      // e o app web. O servico para quando a store refletir a saida, pelo
+      // mesmo caminho de quando se sai pela interface.
+      const { disconnectFn, leaveVoice } = useVoiceStore.getState();
+      if (disconnectFn) void disconnectFn();
+      else leaveVoice();
+    });
+
+    return () => {
+      unsubscribe();
+      removeHangup();
+      // Desmontar nao significa sair da call (a arvore de componentes pode
+      // remontar), mas deixar o servico ligado sem ninguem para desliga-lo
+      // seria pior: uma notificacao permanente que so some matando o app.
+      if (!useVoiceStore.getState().isLiveKitConnected) stopAndroidVoiceService();
+    };
+  }, []);
+
+  return null;
+}