refactor: move SVGs and style.css to static/assets/ and update references

static/assets/readme-logo-dark.svg

@@ -0,0 +1,23 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 100 100" width="100" height="100">
+  <defs>
+    <radialGradient id="bg" cx="35%" cy="35%" r="75%">
+      <stop offset="0%" style="stop-color: var(--accent, #0466c8)" />
+      <stop offset="100%" style="stop-color: var(--accent-dark, #1d4ed8)" />
+    </radialGradient>
+    <clipPath id="clip">
+      <circle cx="50" cy="50" r="45" />
+    </clipPath>
+  </defs>
+
+  <!-- Base -->
+  <circle cx="50" cy="50" r="45" fill="url(#bg)" />
+
+  <!-- Crescent moon cutout -->
+  <g clip-path="url(#clip)">
+    <path
+      d="M70 50a25 25 0 1 1 -25 -25 20 20 0 1 0 25 25z"
+      fill="#FFF7ED"
+      transform="translate(-2 -2)"
+    />
+  </g>
+</svg>