feat: NovaCPX v1.0.0 initial scaffold

Full hosting control panel with 3 tiers: Admin, Reseller, User.
- install.sh: unattended installer for Ubuntu 20/22/24 + Debian 11/12
- PHP multi-version (7.4/8.1/8.2/8.3), Apache2/nginx choice, MySQL, PostgreSQL
- BIND9 DNS, Postfix+Dovecot mail, ProFTPD, Certbot SSL, UFW, Fail2Ban
- 18-table DB schema with audit log and version tracking
- PHP REST API (auth, system/updates, server stats, service control)
- Admin panel: dark dashboard, service manager, git-based update system
- User panel: usage rings + feature card grid (distinct from cPanel)
- VERSION file: git-tracked; Admin > Updates panel shows/applies git commits

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

panel/lib/Response.php

@@ -0,0 +1,29 @@
+<?php
+class Response {
+    public static function json(array $data, int $code = 200): never {
+        http_response_code($code);
+        echo json_encode($data, JSON_UNESCAPED_UNICODE | JSON_UNESCAPED_SLASHES);
+        exit;
+    }
+
+    public static function success(mixed $data = null, string $message = 'OK'): never {
+        self::json(['success' => true, 'message' => $message, 'data' => $data]);
+    }
+
+    public static function error(string $message, int $code = 400, array $errors = []): never {
+        self::json(['success' => false, 'message' => $message, 'errors' => $errors], $code);
+    }
+
+    public static function paginate(array $items, int $total, int $page, int $perPage): never {
+        self::json([
+            'success' => true,
+            'data'    => $items,
+            'meta'    => [
+                'total'    => $total,
+                'page'     => $page,
+                'per_page' => $perPage,
+                'pages'    => (int) ceil($total / $perPage),
+            ],
+        ]);
+    }
+}