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/DB.php

@@ -0,0 +1,43 @@
+<?php
+class DB {
+    private static ?DB $instance = null;
+    private PDO $pdo;
+
+    private function __construct() {
+        $this->pdo = new PDO(
+            "mysql:host=" . DB_HOST . ";dbname=" . DB_NAME . ";charset=utf8mb4",
+            DB_USER, DB_PASS,
+            [
+                PDO::ATTR_ERRMODE            => PDO::ERRMODE_EXCEPTION,
+                PDO::ATTR_DEFAULT_FETCH_MODE => PDO::FETCH_ASSOC,
+                PDO::ATTR_EMULATE_PREPARES   => false,
+            ]
+        );
+    }
+
+    public static function getInstance(): self {
+        if (!self::$instance) self::$instance = new self();
+        return self::$instance;
+    }
+
+    public function execute(string $sql, array $params = []): PDOStatement {
+        $stmt = $this->pdo->prepare($sql);
+        $stmt->execute($params);
+        return $stmt;
+    }
+
+    public function fetchOne(string $sql, array $params = []): ?array {
+        return $this->execute($sql, $params)->fetch() ?: null;
+    }
+
+    public function fetchAll(string $sql, array $params = []): array {
+        return $this->execute($sql, $params)->fetchAll();
+    }
+
+    public function insert(string $sql, array $params = []): string {
+        $this->execute($sql, $params);
+        return $this->pdo->lastInsertId();
+    }
+
+    public function pdo(): PDO { return $this->pdo; }
+}