docs: add VitePress documentation site

- 22 content pages across Guide, Concepts, and Reference sections
- Custom indigo/cyan theme with Lucide icons and Mermaid diagrams
- GitHub Actions workflow for GitHub Pages deployment
- Live preview: https://mempalace-docs.netlify.app/

website/public/icons/search.svg

@@ -0,0 +1,16 @@
+<!-- @license lucide-static v0.468.0 - ISC -->
+<svg
+  class="lucide lucide-search"
+  xmlns="http://www.w3.org/2000/svg"
+  width="24"
+  height="24"
+  viewBox="0 0 24 24"
+  fill="none"
+  stroke="#06b6d4"
+  stroke-width="2"
+  stroke-linecap="round"
+  stroke-linejoin="round"
+>
+  <circle cx="11" cy="11" r="8" />
+  <path d="m21 21-4.3-4.3" />
+</svg>