refactor: Update MQTT test endpoint to use API v1 route

- Modify MQTT test fetch endpoint to use `/api/v1/mqtt/test`
- Align with ongoing route standardization efforts

views/pages/settings/integrationSettings.html

@@ -345,7 +345,7 @@
                         });
 
                         // Create the fetch promise
-                        const fetchPromise = fetch('/mqtt/test', {
+                        const fetchPromise = fetch('/api/v1/mqtt/test', {
                             method: 'POST',
                             headers: {
                                 'Content-Type': 'application/json',