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>

playwright.config.js

@@ -0,0 +1,21 @@
+const { defineConfig } = require('@playwright/test');
+
+module.exports = defineConfig({
+  testDir: './tests',
+  timeout: 90000,
+  retries: 0,
+  use: {
+    baseURL: 'http://localhost:8081',
+    headless: true,
+    viewport: { width: 1280, height: 900 },
+    screenshot: 'only-on-failure',
+  },
+  webServer: {
+    command: 'php -d upload_max_filesize=500M -d post_max_size=512M -d memory_limit=768M -S localhost:8081 router.php',
+    port: 8081,
+    reuseExistingServer: true,
+  },
+  projects: [
+    { name: 'chromium', use: { browserName: 'chromium' } },
+  ],
+});