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/utils/style-helpers.ts

@@ -0,0 +1,16 @@
+import { CSSProperties } from 'react';
+
+const camelToKebab = (str: string): string =>
+  str.replace(/[A-Z]/g, (m) => '-' + m.toLowerCase());
+
+export function cssPropsToString(style: CSSProperties | undefined): string {
+  if (!style) return '';
+  return Object.entries(style)
+    .filter(([, v]) => v !== undefined && v !== null && v !== '')
+    .map(([k, v]) => `${camelToKebab(k)}:${v}`)
+    .join(';');
+}
+
+export function mergeStyles(...styles: (CSSProperties | undefined)[]): CSSProperties {
+  return Object.assign({}, ...styles.filter(Boolean));
+}