feat: initialize React admin build pipeline (F2.1-F2.6)

- Add package.json with @wordpress/scripts and React dependencies
- Configure webpack for admin bundle output
- Create src/admin directory structure (api, components, pages)
- Implement API client with nonce handling (ajaxRequest, apiRequest)
- Add API methods for orders, customers, products, forms, coupons, licenses
- Create React App component with page routing
- Add placeholder page components for all admin sections
- Create ReactAdmin PHP class to manage asset enqueuing
- Register ReactAdmin singleton in main plugin file
- Bump version to 2.0.0

Build: Run 'npm install && npm run build' to generate assets

package.json

@@ -0,0 +1,31 @@
+{
+  "name": "formipay",
+  "version": "2.0.0",
+  "description": "WordPress payment form plugin with React admin interface",
+  "author": "Formipay",
+  "license": "GPL-2.0-or-later",
+  "scripts": {
+    "build": "wp-scripts build",
+    "start": "wp-scripts start",
+    "format": "wp-scripts format",
+    "lint:js": "wp-scripts lint-js",
+    "lint:js:fix": "wp-scripts lint-js --fix",
+    "lint:css": "wp-scripts lint-style",
+    "lint:css:fix": "wp-scripts lint-style --fix",
+    "packages-update": "wp-scripts packages-update"
+  },
+  "devDependencies": {
+    "@wordpress/scripts": "^27.0.0"
+  },
+  "dependencies": {
+    "@wordpress/api-fetch": "^6.0.0",
+    "@wordpress/components": "^25.0.0",
+    "@wordpress/data": "^9.0.0",
+    "@wordpress/date": "^4.0.0",
+    "@wordpress/element": "^5.0.0",
+    "@wordpress/i18n": "^4.0.0",
+    "@wordpress/icons": "^9.0.0",
+    "@wordpress/url": "^8.0.0",
+    "@tanstack/react-table": "^8.11.0"
+  }
+}