Initial commit: Site Builder with PHP API backend

Visual drag-and-drop website builder using GrapesJS with:
- Multi-page editor with live preview
- File-based asset storage via PHP API (no localStorage base64)
- Template library, Docker support, and Playwright test suite

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Dockerfile

@@ -0,0 +1,10 @@
+# Simple nginx container to serve the site builder
+FROM nginx:alpine
+
+# Copy site builder files to nginx html directory
+COPY . /usr/share/nginx/html/
+
+# Expose port 80
+EXPOSE 80
+
+# nginx runs automatically