feat: full-screen incoming call UI over lock screen

Enable proper full-screen call experience when the phone is locked
or the app is in the background:

- CallActivity shows over lock screen (setShowWhenLocked/turnScreenOn)
- Manifest adds showOnLockScreen and turnScreenOn attributes
- Remove setSilent(true) from notification — it was blocking the
  full-screen intent from triggering (channel silence is enough)
- Populate ActiveCallHolder eagerly in initCallController() so the
  full-screen intent can launch CallActivity even when the Compose
  UI is paused in the background

https://claude.ai/code/session_01Ak5tTkujpjNG1r5ASuPipZ

amethyst/src/main/AndroidManifest.xml

@@ -213,6 +213,8 @@
             android:launchMode="singleTop"
             android:exported="false"
             android:resizeableActivity="true"
+            android:showOnLockScreen="true"
+            android:turnScreenOn="true"
             android:theme="@style/Theme.Amethyst"
         />
 

amethyst/src/main/java/com/vitorpamplona/amethyst/service/notifications/NotificationUtils.kt

@@ -602,7 +602,6 @@ object NotificationUtils {
                 .setOngoing(true)
                 .setTimeoutAfter(60_000)
                 .setVisibility(NotificationCompat.VISIBILITY_PUBLIC)
-                .setSilent(true)
                 .addAction(R.drawable.amethyst, stringRes(applicationContext, R.string.call_reject), rejectPendingIntent)
                 .addAction(R.drawable.amethyst, stringRes(applicationContext, R.string.call_accept), acceptPendingIntent)
 

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/call/CallActivity.kt

@@ -70,6 +70,18 @@ class CallActivity : AppCompatActivity() {
         enableEdgeToEdge()
         super.onCreate(savedInstanceState)
 
+        // Show over lock screen and turn screen on for incoming calls
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O_MR1) {
+            setShowWhenLocked(true)
+            setTurnScreenOn(true)
+        } else {
+            @Suppress("DEPRECATION")
+            window.addFlags(
+                android.view.WindowManager.LayoutParams.FLAG_SHOW_WHEN_LOCKED or
+                    android.view.WindowManager.LayoutParams.FLAG_TURN_SCREEN_ON,
+            )
+        }
+
         val callManager = ActiveCallHolder.callManager
         val callController = ActiveCallHolder.callController
         val accountViewModel = ActiveCallHolder.accountViewModel

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/AccountViewModel.kt

@@ -224,6 +224,11 @@ class AccountViewModel(
         callManager.onAnswerReceived = { event -> controller.onCallAnswerReceived(event.sdpAnswer()) }
         callManager.onIceCandidateReceived = { event -> controller.onIceCandidateReceived(event) }
         callController = controller
+
+        // Populate ActiveCallHolder so CallActivity can launch even when the app
+        // is in the background (e.g. full-screen incoming call intent).
+        com.vitorpamplona.amethyst.ui.call.ActiveCallHolder
+            .set(callManager, controller, this)
     }
 
     val eventSync =