feat: rewrite website in PHP, drop Node.js stack

Replace React/Vite frontend + Fastify API with a single PHP application.

- Front controller router in public/index.php (clean URLs via .htaccess)
- Session-based auth (no JWT) — register, login, verify email,
  forgot/reset password, logout
- Stripe checkout sessions, billing portal, webhook handler
  (checkout.session.completed, subscription.updated/deleted)
- License IP change via internal licensing server API
- PHP classes: DB (PDO), Auth, Mailer (PHPMailer), StripeClient
- Views: home, pricing, install, login, register, dashboard,
  verify-email, forgot-password, reset-password, 404
- Tailwind CSS via CDN — no build step required
- Composer dependencies: stripe/stripe-php, phpmailer/phpmailer,
  vlucas/phpdotenv, ramsey/uuid
- CSRF protection on all POST forms
- PRG pattern with session flash messages

Co-Authored-By: Claude Sonnet 4.6 <[email protected]>

composer.json

@@ -0,0 +1,20 @@
+{
+    "name": "nixpanel/website",
+    "description": "NixPanel.io marketing website and customer portal",
+    "type": "project",
+    "require": {
+        "php": ">=8.1",
+        "stripe/stripe-php": "^13.0",
+        "phpmailer/phpmailer": "^6.9",
+        "vlucas/phpdotenv": "^5.6",
+        "ramsey/uuid": "^4.7"
+    },
+    "autoload": {
+        "psr-4": {
+            "NixPanel\\": "src/"
+        }
+    },
+    "config": {
+        "optimize-autoloader": true
+    }
+}