feat: Implement comprehensive multi-channel notification system with templating and SSL monitoring

- Add robust notification system supporting 7+ communication channels with intelligent message templating, resource monitoring, and SSL certificate alerts. Notification Channels: (Telegram, Discord, Slack, Signal, Email, Google Chat, Webhooks).

- This notification system provides enterprise-grade alerting capabilities with extensive customization options and multi-channel redundancy for critical service monitoring.

server/service-operation/monitoring/notification_monitor.go

@@ -0,0 +1,71 @@
+package monitoring
+
+import (
+	"log"
+
+	"service-operation/notification"
+	"service-operation/pocketbase"
+)
+
+// NotificationMonitor handles notification logic for the monitoring service
+type NotificationMonitor struct {
+	notifier     *notification.ServiceNotifier
+	lastStatuses map[string]string // Track last known status for each service
+}
+
+// NewNotificationMonitor creates a new notification monitor
+func NewNotificationMonitor(pbClient *pocketbase.PocketBaseClient) *NotificationMonitor {
+	return &NotificationMonitor{
+		notifier:     notification.NewServiceNotifier(pbClient),
+		lastStatuses: make(map[string]string),
+	}
+}
+
+// CheckAndNotify checks if notification should be sent and sends it
+func (nm *NotificationMonitor) CheckAndNotify(service pocketbase.Service, currentStatus string) {
+	// Skip if no notification configured
+	if service.NotificationID == "" {
+		return
+	}
+
+	// Get last known status
+	lastStatus, exists := nm.lastStatuses[service.ID]
+	
+	// Send notification if:
+	// 1. This is the first check (no previous status)
+	// 2. Status has changed
+	// 3. Service is currently down (always notify for down status)
+	shouldNotify := !exists || lastStatus != currentStatus || currentStatus == "down"
+
+	if shouldNotify {
+		log.Printf("Sending notification for service %s: %s -> %s", service.Name, lastStatus, currentStatus)
+		
+		// Send notification using custom method
+		if err := nm.notifier.NotifyCustom(
+			service.NotificationID,
+			service.TemplateID,
+			service.Name,
+			currentStatus,
+			nm.formatStatusMessage(service, currentStatus),
+		); err != nil {
+			log.Printf("Failed to send notification: %v", err)
+		}
+	}
+
+	// Update last known status
+	nm.lastStatuses[service.ID] = currentStatus
+}
+
+// formatStatusMessage creates a formatted message for the status change
+func (nm *NotificationMonitor) formatStatusMessage(service pocketbase.Service, status string) string {
+	switch status {
+	case "up":
+		return "Service is now operational"
+	case "down":
+		return "Service is currently unavailable"
+	case "warning":
+		return "Service is experiencing issues"
+	default:
+		return "Service status has changed"
+	}
+}