feat: add wireguard secure installer with modular architecture

This commit introduces a new WireGuard VPN installer with enterprise-grade security features. The installer includes:

- Zero-touch installation with automatic configuration
- Modular architecture for maintainability (separate lib files)
- Client management interface with bandwidth monitoring
- Support for multiple Linux distributions
- Secure defaults and hardened configurations

The implementation provides a complete solution for deploying WireGuard VPN servers with minimal user interaction while maintaining security best practices.

lib/utils.sh

@@ -0,0 +1,54 @@
+#!/bin/bash
+# WireGuard Secure Installer
+# Copyright (c) 2025 Muhammad Fadhila Abiyyu Faris
+# GitHub: [github.com/fadhila36/wireguard-secure-installer](https://github.com/fadhila36/wireguard-secure-installer)
+
+# Colors
+RED='\033[0;31m'
+GREEN='\033[0;32m'
+YELLOW='\033[0;33m'
+BLUE='\033[0;34m'
+NC='\033[0m' # No Color
+
+log_info() {
+    echo -e "${GREEN}[INFO]${NC} $1"
+    echo "[INFO] $1" >> "$LOG_FILE"
+}
+
+log_warn() {
+    echo -e "${YELLOW}[WARN]${NC} $1"
+    echo "[WARN] $1" >> "$LOG_FILE"
+}
+
+log_error() {
+    echo -e "${RED}[ERROR]${NC} $1"
+    echo "[ERROR] $1" >> "$LOG_FILE"
+}
+
+fatal_error() {
+    log_error "$1"
+    exit 1
+}
+
+check_root() {
+    if [ "$EUID" -ne 0 ]; then
+        fatal_error "This script must be run as root."
+    fi
+}
+
+show_banner() {
+    clear
+    echo -e "${BLUE}"
+    echo "========================================================================="
+    echo "   WireGuard Secure Installer Enterprise"
+    echo "   (c) 2025 Muhammad Fadhila Abiyyu Faris"
+    echo "   https://github.com/fadhila36/wireguard-secure-installer"
+    echo "========================================================================="
+    echo -e "${NC}"
+}
+
+cleanup() {
+    if [ $? -ne 0 ]; then
+        log_error "An error occurred. Check $LOG_FILE for details."
+    fi
+}