fix: ntfy webhook now sends plain text instead of JSON

- Modified generatePayloadFromTemplate to skip JSON validation for ntfy
- ntfy uses plain text body format, not JSON
- Messages now successfully delivered to ntfy topics
- Headers for title/priority/tags need dynamic templating support (future enhancement)

internal/notifications/notifications.go

@@ -463,7 +463,7 @@ func (n *NotificationManager) sendGroupedWebhook(webhook WebhookConfig, alertLis
 			// The template already has the chat_id embedded
 		}
 		
-		jsonData, err = n.generatePayloadFromTemplate(enhanced.PayloadTemplate, data)
+		jsonData, err = n.generatePayloadFromTemplateWithService(enhanced.PayloadTemplate, data, webhook.Service)
 		if err != nil {
 			log.Error().
 				Err(err).
@@ -539,7 +539,7 @@ func (n *NotificationManager) sendGroupedWebhook(webhook WebhookConfig, alertLis
 				}
 			}
 			
-			jsonData, err = n.generatePayloadFromTemplate(enhanced.PayloadTemplate, data)
+			jsonData, err = n.generatePayloadFromTemplateWithService(enhanced.PayloadTemplate, data, webhook.Service)
 			if err != nil {
 				log.Error().
 					Err(err).
@@ -711,7 +711,7 @@ func (n *NotificationManager) sendWebhook(webhook WebhookConfig, alert *alerts.A
 			}
 		}
 		
-		jsonData, err = n.generatePayloadFromTemplate(enhanced.PayloadTemplate, data)
+		jsonData, err = n.generatePayloadFromTemplateWithService(enhanced.PayloadTemplate, data, webhook.Service)
 		if err != nil {
 			log.Error().
 				Err(err).
@@ -775,7 +775,7 @@ func (n *NotificationManager) sendWebhook(webhook WebhookConfig, alert *alerts.A
 				}
 			}
 			
-			jsonData, err = n.generatePayloadFromTemplate(enhanced.PayloadTemplate, data)
+			jsonData, err = n.generatePayloadFromTemplateWithService(enhanced.PayloadTemplate, data, webhook.Service)
 			if err != nil {
 				log.Error().
 					Err(err).
@@ -841,6 +841,11 @@ func (n *NotificationManager) prepareWebhookData(alert *alerts.Alert, customFiel
 
 // generatePayloadFromTemplate renders the payload using Go templates
 func (n *NotificationManager) generatePayloadFromTemplate(templateStr string, data WebhookPayloadData) ([]byte, error) {
+	return n.generatePayloadFromTemplateWithService(templateStr, data, "")
+}
+
+// generatePayloadFromTemplateWithService renders the payload using Go templates with service-specific handling
+func (n *NotificationManager) generatePayloadFromTemplateWithService(templateStr string, data WebhookPayloadData, service string) ([]byte, error) {
 	// Create template with helper functions
 	funcMap := template.FuncMap{
 		"title": func(s string) string {
@@ -865,7 +870,13 @@ func (n *NotificationManager) generatePayloadFromTemplate(templateStr string, da
 		return nil, fmt.Errorf("template execution failed: %w", err)
 	}
 
-	// Validate that the generated payload is valid JSON
+	// Skip JSON validation for services that use plain text payloads
+	if service == "ntfy" {
+		// ntfy uses plain text, not JSON
+		return buf.Bytes(), nil
+	}
+
+	// Validate that the generated payload is valid JSON for other services
 	var jsonCheck interface{}
 	if err := json.Unmarshal(buf.Bytes(), &jsonCheck); err != nil {
 		log.Error().

internal/notifications/webhook_templates.go

@@ -264,23 +264,24 @@ func GetWebhookTemplates() []WebhookTemplate {
 			Name:       "ntfy.sh",
 			URLPattern: "https://ntfy.sh/{topic}",
 			Method:     "POST",
-			Headers:    map[string]string{"Content-Type": "application/json"},
-			PayloadTemplate: `{
-				"topic": "{{.CustomFields.topic}}",
-				"message": "{{.Message}}",
-				"title": "Pulse Alert: {{.Level | title}}",
-				"priority": {{if eq .Level "critical"}}5{{else if eq .Level "warning"}}4{{else}}3{{end}},
-				"tags": ["{{.Level}}", "{{.Type}}", "pulse"],
-				"click": "{{.Instance}}",
-				"actions": [
-					{
-						"action": "view",
-						"label": "View in Pulse",
-						"url": "{{.Instance}}"
-					}
-				],
-				"markdown": true
-			}`,
+			Headers: map[string]string{
+				"Content-Type": "text/plain",
+				"Title": "Pulse Alert",
+				"Priority": "urgent",
+				"Tags": "pulse,monitoring",
+			},
+			PayloadTemplate: `🚨 {{.Level | title}} Alert: {{.ResourceName}}
+
+{{.Message}}
+
+📊 Details:
+• Node: {{.Node}}
+• Type: {{.Type | title}}
+• Value: {{if or (eq .Type "diskRead") (eq .Type "diskWrite")}}{{printf "%.1f" .Value}} MB/s{{else}}{{printf "%.1f" .Value}}%{{end}}
+• Threshold: {{if or (eq .Type "diskRead") (eq .Type "diskWrite")}}{{printf "%.0f" .Threshold}} MB/s{{else}}{{printf "%.0f" .Threshold}}%{{end}}
+• Duration: {{.Duration}}
+
+View in Pulse: {{.Instance}}`,
 			Instructions: "1. Choose a topic name (e.g., 'my-pulse-alerts')\n2. URL format: https://ntfy.sh/YOUR_TOPIC\n   Or for self-hosted: https://your-ntfy-server/YOUR_TOPIC\n3. Optional: Add authentication token in headers if required\n4. Subscribe to the topic in your ntfy app using the same topic name",
 		},
 		{