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.

docs/images/ferese-lockup.svg

@@ -1,24 +0,0 @@
-<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 300 80" role="img" aria-labelledby="title desc">
-  <title id="title">Ferese</title>
-  <desc id="desc">The blue Ferese symbol beside the Ferese wordmark</desc>
-
-  <defs>
-    <linearGradient id="mark" x1="0%" y1="0%" x2="100%" y2="100%">
-      <stop offset="0%" stop-color="#6ea3ff"/>
-      <stop offset="100%" stop-color="#3d7be6"/>
-    </linearGradient>
-    <style>
-      .wordmark { fill: #1c1d21; }
-      @media (prefers-color-scheme: dark) {
-        .wordmark { fill: #f2f2f7; }
-      }
-    </style>
-  </defs>
-
-  <g transform="translate(0 8) scale(.32)" fill="url(#mark)">
-    <rect x="20" y="20" width="50" height="160" rx="8"/>
-    <rect x="80" y="20" width="100" height="55" rx="8"/>
-    <rect x="80" y="95" width="70" height="45" rx="8"/>
-  </g>
-  <text class="wordmark" x="78" y="56" font-family="-apple-system, BlinkMacSystemFont, Helvetica, Arial, sans-serif" font-size="48" font-weight="700">Ferese</text>
-</svg>