Replace the SkyPress mark with the new winged-sun logo
Swap the hand-drawn type-block mark for the new winged-sun logo across
the favicon and every in-app spot (Logo.astro, AppBar, LoadingScene).
The mark now lives once in src/lib/brand/skypress-mark.ts as inline SVG
whose paths use fill="currentColor", so it follows the surrounding color
(the --sun token, which lightens in dark mode) instead of being locked to
one orange. A single source avoids duplicating the path data across the
Astro/React island boundary. The favicon keeps the static-orange
public/skypress-logo.svg, since a favicon can't inherit currentColor.
This drops the landing-only sun->moon easter-egg: the new logo is a sun
with no moon variant and only one asset was provided. Its night/dusk swap
styles in index.astro and the three tests that locked it are removed.