Update branding

Update the Ferese symbols, appearance-specific wallpapers, and rounded wallpaper and theme previews. Bundle Figtree and add the Ferese name to the website header.

Verified configuration, theme, Settings, wallpaper and installer tests, both UI renderers, the static site build, and browser layouts.

site/README.md

@@ -35,3 +35,20 @@ The site uses relative links, including for handbook search, so it also works un
 
 For deployment setup, follow [GitHub’s custom workflow
 documentation](https://docs.github.com/en/pages/getting-started-with-github-pages/using-custom-workflows-with-github-pages).
+
+## Brand assets
+
+The Ferese symbols live in `assets/branding`. The website uses
+`ferese-blue-dark.svg`. The README chooses the light or dark SVG to match
+the reader's appearance and uses the flat blue SVG as its fallback. Keep their
+1024×1024 canvas square so the symbol and glow are not stretched or cropped.
+
+The favicon uses the flat blue symbol. `site/assets/favicon-32.png` is 32×32;
+`site/assets/favicon.ico` contains 16×16, 32×32 and 48×48 images. These files are
+checked in, so building the site needs no icon renderer. Their links work at
+both the site root and the GitHub Pages project path.
+
+The light and dark wallpapers live in `assets/wallpapers`. Both are
+3840×2160 and are bundled by the installer. Ferese selects the matching image
+when no custom wallpaper is set. Settings keeps both defaults available below
+the current wallpaper preview. Existing screenshots show the previous artwork.