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]>

api/.env.example

@@ -1,44 +0,0 @@
-# Server
-NODE_ENV=production
-PORT=4000
-HOST=0.0.0.0
-
-# CORS
-CORS_ORIGIN=https://nixpanel.io
-
-# Database (MariaDB / MySQL)
-DB_HOST=127.0.0.1
-DB_PORT=3306
-DB_USER=nixpanel_web
-DB_PASSWORD=your_secure_password_here
-DB_NAME=nixpanel_website
-
-# JWT — generate with: openssl rand -hex 64
-JWT_SECRET=changeme_use_openssl_rand_hex_64
-JWT_EXPIRES_IN=7d
-
-# Stripe
-STRIPE_SECRET_KEY=sk_live_...
-STRIPE_WEBHOOK_SECRET=whsec_...
-
-# Stripe Price IDs (create in Stripe Dashboard)
-STRIPE_PRICE_SOLO_MONTHLY=price_...
-STRIPE_PRICE_SOLO_ANNUAL=price_...
-STRIPE_PRICE_HOST_MONTHLY=price_...
-STRIPE_PRICE_HOST_ANNUAL=price_...
-STRIPE_PRICE_AGENCY_MONTHLY=price_...
-STRIPE_PRICE_AGENCY_ANNUAL=price_...
-
-# Internal link to the licensing server
-LICENSING_SERVER_URL=http://localhost:3000
-LICENSING_SERVER_API_KEY=your_internal_api_key_here
-
-# Email (SMTP)
-MAIL_HOST=smtp.mailgun.org
-MAIL_PORT=587
-MAIL_USER=[email protected]
-MAIL_PASSWORD=your_smtp_password
-MAIL_FROM=[email protected]
-
-# Public URL (used in emails and redirects)
-APP_URL=https://nixpanel.io