android: refresh adaptive launcher icon

Add density-specific launcher PNGs with a new foreground, a monochrome
layer for themed icons, and a light background; drop the old vector
foreground.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

android/app/src/main/res/mipmap-anydpi-v26/ic_launcher_round.xml

@@ -1,5 +1,6 @@
 <?xml version="1.0" encoding="utf-8"?>
 <adaptive-icon xmlns:android="http://schemas.android.com/apk/res/android">
     <background android:drawable="@color/ic_launcher_background" />
-    <foreground android:drawable="@drawable/ic_launcher_foreground" />
+    <foreground android:drawable="@mipmap/ic_launcher_foreground" />
+    <monochrome android:drawable="@mipmap/ic_launcher_monochrome" />
 </adaptive-icon>