Add Craft.js site builder (v2) - complete rebuild from GrapesJS

Rebuilt the visual site builder from scratch using Craft.js, React 18,
and TypeScript. The new editor renders directly in the DOM (no iframe),
supports 40+ components, multi-page with shared header/footer, 16
templates, full-spectrum color/gradient controls, custom head code
injection, save/publish workflow, and auto-save.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

craft/src/main.tsx

@@ -0,0 +1,14 @@
+import React from 'react';
+import ReactDOM from 'react-dom/client';
+import { App } from './App';
+import { WhpConfig } from './types';
+import './styles/editor.css';
+
+// Read WHP_CONFIG injected by PHP wrapper (or null for standalone dev)
+const whpConfig: WhpConfig | null = (window as any).WHP_CONFIG || null;
+
+ReactDOM.createRoot(document.getElementById('root')!).render(
+  <React.StrictMode>
+    <App whpConfig={whpConfig} />
+  </React.StrictMode>
+);