Add Marketplace icon, banner and README screenshot

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

media/icon.svg

@@ -0,0 +1,23 @@
+<svg xmlns="http://www.w3.org/2000/svg" width="256" height="256" viewBox="0 0 256 256">
+  <defs>
+    <linearGradient id="bg" x1="0" y1="0" x2="1" y2="1">
+      <stop offset="0" stop-color="#0e7490"/>
+      <stop offset="1" stop-color="#3730a3"/>
+    </linearGradient>
+  </defs>
+  <rect x="8" y="8" width="240" height="240" rx="52" fill="url(#bg)"/>
+  <g fill="none" stroke="#e0f2fe" stroke-width="9" stroke-linecap="round" stroke-linejoin="round">
+    <path d="M78 98 V128 H178 V98"/>
+    <path d="M128 128 V160"/>
+  </g>
+  <g fill="#ffffff">
+    <rect x="42" y="54" width="72" height="46" rx="11"/>
+    <rect x="142" y="54" width="72" height="46" rx="11"/>
+    <rect x="92" y="158" width="72" height="46" rx="11" fill="#fde68a"/>
+  </g>
+  <g fill="#0e7490">
+    <rect x="56" y="72" width="44" height="9" rx="4.5"/>
+    <rect x="156" y="72" width="44" height="9" rx="4.5"/>
+  </g>
+  <rect x="106" y="176" width="44" height="9" rx="4.5" fill="#92400e"/>
+</svg>