feat(settings): add webhook test functionality

- Add test button to webhook settings dialog
- Implement webhook test API endpoint
- Replace alert with notification system
- Style test button to match existing UI

src/api/index.js

@@ -41,7 +41,9 @@ export const systemApi = {
         return api.get(url);
     },
     setSettings: (settings) => 
-        api.post('/system/settings/set', settings)
+        api.post('/system/settings/set', settings),
+    testWebhook: (webhookConfig) => 
+        api.post('/system/webhook/test', webhookConfig)
 };
 
 export const authApi = {