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/24/outline/CubeTransparentIcon.js

@@ -0,0 +1,26 @@
+const React = require("react");
+function CubeTransparentIcon({
+  title,
+  titleId,
+  ...props
+}, svgRef) {
+  return /*#__PURE__*/React.createElement("svg", Object.assign({
+    xmlns: "http://www.w3.org/2000/svg",
+    fill: "none",
+    viewBox: "0 0 24 24",
+    strokeWidth: 1.5,
+    stroke: "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", {
+    strokeLinecap: "round",
+    strokeLinejoin: "round",
+    d: "m21 7.5-2.25-1.313M21 7.5v2.25m0-2.25-2.25 1.313M3 7.5l2.25-1.313M3 7.5l2.25 1.313M3 7.5v2.25m9 3 2.25-1.313M12 12.75l-2.25-1.313M12 12.75V15m0 6.75 2.25-1.313M12 21.75V19.5m0 2.25-2.25-1.313m0-16.875L12 2.25l2.25 1.313M21 14.25v2.25l-2.25 1.313m-13.5 0L3 16.5v-2.25"
+  }));
+}
+const ForwardRef = /*#__PURE__*/ React.forwardRef(CubeTransparentIcon);
+module.exports = ForwardRef;