docs(design): remove SVG, use PNG logo only

SVG icon is no longer in use. public/logo.png (1024x1024 RGBA) is
the single logo asset. DESIGN.md updated accordingly: SVG snippet
removed, wordmark pattern and <head> references updated to PNG.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

node_modules/@heroicons/react/16/solid/WalletIcon.js

@@ -0,0 +1,22 @@
+const React = require("react");
+function WalletIcon({
+  title,
+  titleId,
+  ...props
+}, svgRef) {
+  return /*#__PURE__*/React.createElement("svg", Object.assign({
+    xmlns: "http://www.w3.org/2000/svg",
+    viewBox: "0 0 16 16",
+    fill: "currentColor",
+    "aria-hidden": "true",
+    "data-slot": "icon",
+    ref: svgRef,
+    "aria-labelledby": titleId
+  }, props), title ? /*#__PURE__*/React.createElement("title", {
+    id: titleId
+  }, title) : null, /*#__PURE__*/React.createElement("path", {
+    d: "M2 3.5A1.5 1.5 0 0 1 3.5 2h9A1.5 1.5 0 0 1 14 3.5v.401a2.986 2.986 0 0 0-1.5-.401h-9c-.546 0-1.059.146-1.5.401V3.5ZM3.5 5A1.5 1.5 0 0 0 2 6.5v.401A2.986 2.986 0 0 1 3.5 6.5h9c.546 0 1.059.146 1.5.401V6.5A1.5 1.5 0 0 0 12.5 5h-9ZM8 10a2 2 0 0 0 1.938-1.505c.068-.268.286-.495.562-.495h2A1.5 1.5 0 0 1 14 9.5v3a1.5 1.5 0 0 1-1.5 1.5h-9A1.5 1.5 0 0 1 2 12.5v-3A1.5 1.5 0 0 1 3.5 8h2c.276 0 .494.227.562.495A2 2 0 0 0 8 10Z"
+  }));
+}
+const ForwardRef = /*#__PURE__*/ React.forwardRef(WalletIcon);
+module.exports = ForwardRef;