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/esm/RectangleGroupIcon.js

@@ -0,0 +1,22 @@
+import * as React from "react";
+function RectangleGroupIcon({
+  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: "M1 4a1 1 0 0 1 1-1h5a1 1 0 0 1 1 1v3a1 1 0 0 1-1 1H2a1 1 0 0 1-1-1V4ZM10 5a1 1 0 0 1 1-1h3a1 1 0 0 1 1 1v6a1 1 0 0 1-1 1h-3a1 1 0 0 1-1-1V5ZM4 10a1 1 0 0 0-1 1v1a1 1 0 0 0 1 1h4a1 1 0 0 0 1-1v-1a1 1 0 0 0-1-1H4Z"
+  }));
+}
+const ForwardRef = /*#__PURE__*/ React.forwardRef(RectangleGroupIcon);
+export default ForwardRef;