The Android Studio template robot was still shipping as the app icon
and as the splash mark. Ports the layered-squares glyph the login
hero uses (LoginScreen.StackLogoGlyph) into the launcher + splash
slots so the app's branding is consistent from the launcher tap
through to the first Compose frame.

  * ic_launcher_foreground: brand glyph sized for the adaptive-icon
    safe zone (central 66dp of a 108dp viewport) so the corners
    survive round / squircle launcher masks.
  * ic_launcher_background: solid SurfaceBase (#0B0B12) plate that
    matches the window background, so the splash-to-content
    transition doesn't flash a different color.
  * ic_launcher_monochrome: single-tint variant for Android 13+
    themed icons (the previous adaptive-icon XML pointed monochrome
    at the colored foreground, which the platform can't recolor
    cleanly).
  * ic_brand_splash: standalone splash glyph that fills the full
    108dp viewport. The launcher foreground has to keep its content
    inside the safe zone and would render visibly small in the
    SplashScreen API icon area (no mask is applied there); this
    drawable expands the same three squares so the splash reads as
    the Stack mark instead of a tiny inset.
  * themes.xml: splash theme now points at ic_brand_splash.

Legacy mipmap-{m,h,xh,xxh,xxxh}dpi PNGs are untouched. They only
ship to API 24-25 devices that can't load the adaptive-icon XML
(min SDK is 24, so the fallback is required); generating new PNGs
from the vector needs a build-time tool that isn't wired in yet.