The manifest referenced the stock platform icon (@android:drawable/sym_def_app_icon),
so the launcher showed a default Android glyph. Added a real icon:
- mipmap-{m,h,xh,xxh,xxxh}dpi/ic_launcher.png + ic_launcher_round.png (48-192 px)
- mipmap-*dpi/ic_launcher_foreground.png (108-432 px, transparent)
- drawable/ic_launcher_background.xml (violet gradient #9B6BFF -> #6D28D9 -> #3B1A91)
- mipmap-anydpi-v26/ic_launcher(.xml|_round.xml) adaptive icon
- manifest: android:icon -> @mipmap/ic_launcher, add android:roundIcon