feat(live): keep screen awake while watching a live stream

Add FLAG_KEEP_SCREEN_ON to the host activity window while
LiveStreamScreen is composed, mirroring the behavior already used by
the fullscreen video player. The flag is cleared on dispose so it
does not leak to other screens.

app/src/main/kotlin/com/wisp/app/ui/screen/LiveStreamScreen.kt

@@ -53,6 +53,7 @@ import androidx.compose.material3.Text
 import androidx.compose.material3.TopAppBar
 import androidx.compose.material3.TopAppBarDefaults
 import androidx.compose.runtime.Composable
+import androidx.compose.runtime.DisposableEffect
 import androidx.compose.runtime.LaunchedEffect
 import androidx.compose.runtime.collectAsState
 import androidx.compose.runtime.getValue
@@ -147,6 +148,15 @@ fun LiveStreamScreen(
         }
     }
 
+    val context = LocalContext.current
+    DisposableEffect(context) {
+        val window = context.findHostActivity()?.window
+        window?.addFlags(android.view.WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON)
+        onDispose {
+            window?.clearFlags(android.view.WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON)
+        }
+    }
+
     Column(modifier = Modifier.fillMaxSize()) {
         // Top bar
         TopAppBar(
@@ -1088,3 +1098,12 @@ private fun formatZapSats(sats: Long): String = when {
     sats >= 1_000 -> "${"%.1f".format(sats / 1_000.0)}k"
     else -> sats.toString()
 }
+
+private fun android.content.Context.findHostActivity(): android.app.Activity? {
+    var ctx: android.content.Context = this
+    while (ctx is android.content.ContextWrapper) {
+        if (ctx is android.app.Activity) return ctx
+        ctx = ctx.baseContext
+    }
+    return null
+}