feat: wakelock for background calls, server selector UI

- Partial wake lock + WiFi high-perf lock during calls — audio
  continues when screen is off / phone is locked
- Server selector: toggle between LAN (172.16.81.175) and Pangolin
  (pangolin.manko.yoga) before connecting
- Room name editable in idle screen

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

android/app/src/main/java/com/wzp/ui/call/CallActivity.kt

@@ -2,7 +2,9 @@ package com.wzp.ui.call
 
 import android.Manifest
 import android.content.pm.PackageManager
+import android.net.wifi.WifiManager
 import android.os.Bundle
+import android.os.PowerManager
 import android.widget.Toast
 import androidx.activity.ComponentActivity
 import androidx.activity.compose.setContent
@@ -21,13 +23,16 @@ import androidx.core.content.ContextCompat
 /**
  * Main activity hosting the in-call Compose UI.
  *
- * Shows the call screen. Does NOT auto-start a call — the user must
+ * Acquires a partial wake lock and WiFi lock during calls to prevent
- * tap "Connect" in the UI.
+ * audio from stopping when the screen turns off.
  */
 class CallActivity : ComponentActivity() {
 
     private val viewModel: CallViewModel by viewModels()
 
+    private var wakeLock: PowerManager.WakeLock? = null
+    private var wifiLock: WifiManager.WifiLock? = null
+
     private val audioPermissionLauncher = registerForActivityResult(
         ActivityResultContracts.RequestPermission()
     ) { granted ->
@@ -40,6 +45,7 @@ class CallActivity : ComponentActivity() {
         super.onCreate(savedInstanceState)
 
         viewModel.setContext(this)
+        viewModel.setWakeLockCallbacks(::acquireWakeLocks, ::releaseWakeLocks)
 
         setContent {
             WzpTheme {
@@ -52,7 +58,6 @@ class CallActivity : ComponentActivity() {
             }
         }
 
-        // Request audio permission proactively but don't start a call
         if (ContextCompat.checkSelfPermission(this, Manifest.permission.RECORD_AUDIO)
             != PackageManager.PERMISSION_GRANTED
         ) {
@@ -60,8 +65,33 @@ class CallActivity : ComponentActivity() {
         }
     }
 
+    private fun acquireWakeLocks() {
+        if (wakeLock == null) {
+            val pm = getSystemService(POWER_SERVICE) as PowerManager
+            wakeLock = pm.newWakeLock(
+                PowerManager.PARTIAL_WAKE_LOCK,
+                "wzp:call"
+            ).apply { acquire() }
+        }
+        if (wifiLock == null) {
+            val wm = applicationContext.getSystemService(WIFI_SERVICE) as WifiManager
+            wifiLock = wm.createWifiLock(
+                WifiManager.WIFI_MODE_FULL_HIGH_PERF,
+                "wzp:call"
+            ).apply { acquire() }
+        }
+    }
+
+    private fun releaseWakeLocks() {
+        wakeLock?.let { if (it.isHeld) it.release() }
+        wakeLock = null
+        wifiLock?.let { if (it.isHeld) it.release() }
+        wifiLock = null
+    }
+
     override fun onDestroy() {
         super.onDestroy()
+        releaseWakeLocks()
         if (isFinishing) {
             viewModel.stopCall()
         }

android/app/src/main/java/com/wzp/ui/call/CallViewModel.kt

@@ -21,6 +21,8 @@ class CallViewModel : ViewModel(), WzpCallback {
     private var engineInitialized = false
     private var audioPipeline: AudioPipeline? = null
     private var audioStarted = false
+    private var acquireWakeLocks: (() -> Unit)? = null
+    private var releaseWakeLocks: (() -> Unit)? = null
 
     private val _callState = MutableStateFlow(0)
     val callState: StateFlow<Int> get() = _callState.asStateFlow()
@@ -43,24 +45,41 @@ class CallViewModel : ViewModel(), WzpCallback {
     private val _roomName = MutableStateFlow(DEFAULT_ROOM)
     val roomName: StateFlow<String> = _roomName.asStateFlow()
 
+    private val _selectedServer = MutableStateFlow(0) // index into SERVERS
+    val selectedServer: StateFlow<Int> = _selectedServer.asStateFlow()
+
     private var statsJob: Job? = null
 
     companion object {
-        const val DEFAULT_RELAY = "pangolin.manko.yoga:4433"
+        val SERVERS = listOf(
+            "172.16.81.175:4433" to "LAN (172.16.81.175)",
+            "pangolin.manko.yoga:4433" to "Pangolin (remote)",
+        )
         const val DEFAULT_ROOM = "android"
     }
 
-    /** Must be called once with Activity context before startCall. */
     fun setContext(context: Context) {
         if (audioPipeline == null) {
             audioPipeline = AudioPipeline(context.applicationContext)
         }
     }
 
-    fun startCall(
+    fun setWakeLockCallbacks(acquire: () -> Unit, release: () -> Unit) {
-        relayAddr: String = DEFAULT_RELAY,
+        acquireWakeLocks = acquire
-        room: String = _roomName.value
+        releaseWakeLocks = release
-    ) {
+    }
+
+    fun selectServer(index: Int) {
+        if (index in SERVERS.indices) {
+            _selectedServer.value = index
+        }
+    }
+
+    fun setRoomName(name: String) { _roomName.value = name }
+
+    fun startCall() {
+        val relay = SERVERS[_selectedServer.value].first
+        val room = _roomName.value
         try {
             if (engine == null) {
                 engine = WzpEngine(this)
@@ -69,24 +88,28 @@ class CallViewModel : ViewModel(), WzpCallback {
                 engine?.init()
                 engineInitialized = true
             }
-            _callState.value = 1 // Connecting
+            _callState.value = 1
+            acquireWakeLocks?.invoke()
             startStatsPolling()
 
             viewModelScope.launch(kotlinx.coroutines.Dispatchers.IO) {
                 try {
-                    val result = engine?.startCall(relayAddr, room) ?: -1
+                    val result = engine?.startCall(relay, room) ?: -1
                     if (result != 0) {
                         _callState.value = 0
                         _errorMessage.value = "Failed to start call (code $result)"
+                        releaseWakeLocks?.invoke()
                     }
                 } catch (e: Exception) {
                     _callState.value = 0
                     _errorMessage.value = "Engine error: ${e.message}"
+                    releaseWakeLocks?.invoke()
                 }
             }
         } catch (e: Exception) {
             _callState.value = 0
             _errorMessage.value = "Engine error: ${e.message}"
+            releaseWakeLocks?.invoke()
         }
     }
 
@@ -97,6 +120,7 @@ class CallViewModel : ViewModel(), WzpCallback {
             engine?.stopCall()
         } catch (_: Exception) {}
         _callState.value = 0
+        releaseWakeLocks?.invoke()
     }
 
     fun toggleMute() {
@@ -113,8 +137,6 @@ class CallViewModel : ViewModel(), WzpCallback {
 
     fun clearError() { _errorMessage.value = null }
 
-    fun setRoomName(name: String) { _roomName.value = name }
-
     // WzpCallback
     override fun onCallStateChanged(state: Int) { _callState.value = state }
     override fun onQualityTierChanged(tier: Int) { _qualityTier.value = tier }
@@ -142,11 +164,9 @@ class CallViewModel : ViewModel(), WzpCallback {
                     if (json.isNotEmpty()) {
                         val s = CallStats.fromJson(json)
                         _stats.value = s
-                        // Sync call state from native engine stats
                         if (s.state != 0) {
                             _callState.value = s.state
                         }
-                        // Start audio pipeline when call becomes active
                         if (s.state == 2 && !audioStarted) {
                             startAudio()
                         }
@@ -166,6 +186,7 @@ class CallViewModel : ViewModel(), WzpCallback {
         super.onCleared()
         stopAudio()
         stopStatsPolling()
+        releaseWakeLocks?.invoke()
         try {
             engine?.stopCall()
             engine?.destroy()

android/app/src/main/java/com/wzp/ui/call/InCallScreen.kt

@@ -50,6 +50,7 @@ fun InCallScreen(
     val qualityTier by viewModel.qualityTier.collectAsState()
     val errorMessage by viewModel.errorMessage.collectAsState()
     val roomName by viewModel.roomName.collectAsState()
+    val selectedServer by viewModel.selectedServer.collectAsState()
 
     Surface(
         modifier = Modifier.fillMaxSize(),
@@ -80,11 +81,44 @@ fun InCallScreen(
                 // Idle — show connect button
                 Spacer(modifier = Modifier.height(48.dp))
 
+                // Server selector
                 Text(
-                    text = "Relay: ${CallViewModel.DEFAULT_RELAY}",
+                    text = "Server",
-                    style = MaterialTheme.typography.bodyMedium,
+                    style = MaterialTheme.typography.labelSmall,
                     color = MaterialTheme.colorScheme.onSurfaceVariant
                 )
+                Spacer(modifier = Modifier.height(4.dp))
+                Row(
+                    modifier = Modifier.fillMaxWidth(),
+                    horizontalArrangement = Arrangement.Center
+                ) {
+                    CallViewModel.SERVERS.forEachIndexed { idx, (_, label) ->
+                        val isSelected = selectedServer == idx
+                        FilledTonalIconButton(
+                            onClick = { viewModel.selectServer(idx) },
+                            modifier = Modifier
+                                .padding(horizontal = 4.dp)
+                                .height(36.dp)
+                                .width(140.dp),
+                            shape = RoundedCornerShape(8.dp),
+                            colors = if (isSelected) {
+                                IconButtonDefaults.filledTonalIconButtonColors(
+                                    containerColor = MaterialTheme.colorScheme.primaryContainer,
+                                    contentColor = MaterialTheme.colorScheme.onPrimaryContainer
+                                )
+                            } else {
+                                IconButtonDefaults.filledTonalIconButtonColors()
+                            }
+                        ) {
+                            Text(
+                                text = label,
+                                style = MaterialTheme.typography.labelSmall,
+                                maxLines = 1
+                            )
+                        }
+                    }
+                }
+
                 Spacer(modifier = Modifier.height(8.dp))
                 OutlinedTextField(
                     value = roomName,
@@ -94,7 +128,7 @@ fun InCallScreen(
                     modifier = Modifier.fillMaxWidth(0.6f)
                 )
 
-                Spacer(modifier = Modifier.height(32.dp))
+                Spacer(modifier = Modifier.height(24.dp))
 
                 Button(
                     onClick = { viewModel.startCall() },