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]>

views/register.php

@@ -0,0 +1,45 @@
+<?php $pageTitle = 'Create Account — NixPanel'; ?>
+
+<div class="min-h-[80vh] flex items-center justify-center px-4 py-16">
+    <div class="w-full max-w-md">
+        <div class="text-center mb-8">
+            <h1 class="text-3xl font-bold text-white">Create your account</h1>
+            <p class="text-gray-400 mt-2">Get started with NixPanel for free</p>
+        </div>
+
+        <div class="card">
+            <form method="POST" action="/register" class="space-y-4">
+                <?= csrf_field() ?>
+
+                <div>
+                    <label class="block text-sm text-gray-400 mb-1.5">Full name</label>
+                    <input type="text" name="full_name" value="<?= old('full_name') ?>" required
+                        class="input" placeholder="Jane Smith">
+                </div>
+
+                <div>
+                    <label class="block text-sm text-gray-400 mb-1.5">Email address</label>
+                    <input type="email" name="email" value="<?= old('email') ?>" required
+                        class="input" placeholder="[email protected]">
+                </div>
+
+                <div>
+                    <label class="block text-sm text-gray-400 mb-1.5">Password</label>
+                    <input type="password" name="password" required minlength="8"
+                        class="input" placeholder="Min 8 characters">
+                </div>
+
+                <button type="submit" class="btn-primary w-full justify-center py-3">Create account</button>
+
+                <p class="text-xs text-gray-500 text-center">
+                    By creating an account you agree to our
+                    <a href="/terms" class="text-brand-400 hover:underline">Terms of Service</a>.
+                </p>
+            </form>
+        </div>
+
+        <p class="text-center text-sm text-gray-500 mt-6">
+            Already have an account? <a href="/login" class="text-brand-400 hover:underline">Sign in</a>
+        </p>
+    </div>
+</div>