Add Heguang Tongkun landing page with light theme and refined UI.

Ship the full Vite/React marketing site with white-background styling, softer gradients, rounded typography, and section layout updates from the design pass.

Co-authored-by: Cursor <cursoragent@cursor.com>

public/icon.svg

@@ -0,0 +1,12 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 32 32">
+  <defs>
+    <linearGradient id="g" x1="0" y1="0" x2="32" y2="32" gradientUnits="userSpaceOnUse">
+      <stop offset="0%" stop-color="#38BDF8"/>
+      <stop offset="100%" stop-color="#8B5CF6"/>
+    </linearGradient>
+  </defs>
+  <rect width="32" height="32" rx="7" fill="#05070F"/>
+  <path d="M16 5 L26 10.5 V21.5 L16 27 L6 21.5 V10.5 Z" fill="none" stroke="url(#g)" stroke-width="1.5"/>
+  <path d="M16 5 L16 16 M16 16 L26 10.5 M16 16 L6 10.5 M16 16 L16 27" stroke="url(#g)" stroke-width="1.1" opacity="0.85"/>
+  <circle cx="16" cy="16" r="1.6" fill="url(#g)"/>
+</svg>