feat: Add comprehensive auto-sync functionality

✨ New Features:
- Auto-sync service with configurable intervals (15min, 30min, 1hour, 6hours, 12hours, 24hours, custom cron)
- Automatic JSON file synchronization from GitHub repositories
- Auto-download new scripts when JSON files are updated
- Auto-update existing scripts when newer versions are available
- Apprise notification service integration for sync status updates
- Comprehensive error handling and logging

🔧 Technical Implementation:
- AutoSyncService: Core scheduling and execution logic
- GitHubJsonService: Handles JSON file synchronization from GitHub
- AppriseService: Sends notifications via multiple channels (Discord, Telegram, Email, Slack, etc.)
- ScriptDownloaderService: Manages automatic script downloads and updates
- Settings API: RESTful endpoints for auto-sync configuration
- UI Integration: Settings modal with auto-sync configuration options

📋 Configuration Options:
- Enable/disable auto-sync functionality
- Flexible scheduling (predefined intervals or custom cron expressions)
- Selective script processing (new downloads, updates, or both)
- Notification settings with multiple Apprise URL support
- Environment-based configuration with .env file persistence

🎯 Benefits:
- Keeps script repository automatically synchronized
- Reduces manual maintenance overhead
- Provides real-time notifications of sync status
- Supports multiple notification channels
- Configurable to match different deployment needs

This feature significantly enhances the automation capabilities of PVE Scripts Local,
making it a truly hands-off solution for script management.

src/server/lib/autoSyncInit.js

@@ -0,0 +1,65 @@
+import { AutoSyncService } from '../services/autoSyncService.js';
+
+let autoSyncService = null;
+
+/**
+ * Initialize auto-sync service and schedule cron job if enabled
+ */
+export function initializeAutoSync() {
+  try {
+    console.log('Initializing auto-sync service...');
+    autoSyncService = new AutoSyncService();
+    
+    // Load settings and schedule if enabled
+    const settings = autoSyncService.loadSettings();
+    
+    if (settings.autoSyncEnabled) {
+      console.log('Auto-sync is enabled, scheduling cron job...');
+      autoSyncService.scheduleAutoSync();
+    } else {
+      console.log('Auto-sync is disabled');
+    }
+    
+    console.log('Auto-sync service initialized successfully');
+  } catch (error) {
+    console.error('Failed to initialize auto-sync service:', error);
+  }
+}
+
+/**
+ * Stop auto-sync service and clean up cron jobs
+ */
+export function stopAutoSync() {
+  try {
+    if (autoSyncService) {
+      console.log('Stopping auto-sync service...');
+      autoSyncService.stopAutoSync();
+      autoSyncService = null;
+      console.log('Auto-sync service stopped');
+    }
+  } catch (error) {
+    console.error('Error stopping auto-sync service:', error);
+  }
+}
+
+/**
+ * Get the auto-sync service instance
+ */
+export function getAutoSyncService() {
+  return autoSyncService;
+}
+
+/**
+ * Graceful shutdown handler
+ */
+export function setupGracefulShutdown() {
+  const shutdown = (signal) => {
+    console.log(`Received ${signal}, shutting down gracefully...`);
+    stopAutoSync();
+    process.exit(0);
+  };
+
+  process.on('SIGTERM', () => shutdown('SIGTERM'));
+  process.on('SIGINT', () => shutdown('SIGINT'));
+  process.on('SIGUSR2', () => shutdown('SIGUSR2')); // For nodemon
+}