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/building-2.svg

@@ -0,0 +1,21 @@
+<!-- @license lucide-static v0.468.0 - ISC -->
+<svg
+  class="lucide lucide-building-2"
+  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"
+>
+  <path d="M6 22V4a2 2 0 0 1 2-2h8a2 2 0 0 1 2 2v18Z" />
+  <path d="M6 12H4a2 2 0 0 0-2 2v6a2 2 0 0 0 2 2h2" />
+  <path d="M18 9h2a2 2 0 0 1 2 2v9a2 2 0 0 1-2 2h-2" />
+  <path d="M10 6h4" />
+  <path d="M10 10h4" />
+  <path d="M10 14h4" />
+  <path d="M10 18h4" />
+</svg>