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/templates/index.ts

@@ -0,0 +1,9 @@
+export type {
+  TemplateDefinition,
+  TemplateComponent,
+  TemplatePageContent,
+  TemplatePageDef,
+  TemplateCategory,
+} from './definitions';
+
+export { allTemplates } from './definitions';