feat: Support multiple notification channels

- Update the Notification Settings dashboard to allow users to select multiple notification channels for alerts.
- Add webhook to notification channels: Add webhook as a selectable option in the notification channel type dropdown.
- Implement template type selection in the Add Template dialog. Based on the selected type.

application/src/components/settings/notification-settings/NotificationSettings.tsx

@@ -87,6 +87,7 @@ const NotificationSettings = () => {
             <TabsTrigger value="slack">Slack</TabsTrigger>
             <TabsTrigger value="signal">Signal</TabsTrigger>
             <TabsTrigger value="email">Email</TabsTrigger>
+            <TabsTrigger value="webhook">Webhook</TabsTrigger>
           </TabsList>
           
           <TabsContent value={currentTab} className="mt-0">
@@ -114,4 +115,4 @@ const NotificationSettings = () => {
   );
 };
 
-export default NotificationSettings;
+export default NotificationSettings;