Add health check endpoint and refactor integration response handling

- Introduced a new public health check endpoint at `api/ping/` to verify API responsiveness.
- Refactored integration response handling to utilize a unified success and error response format across various methods in `IntegrationSettingsViewSet`, improving consistency and clarity in API responses.
- Updated URL patterns to include the new ping endpoint and adjusted imports accordingly.

frontend/src/components/common/ImageGenerationCard.tsx

@@ -138,6 +138,8 @@ export default function ImageGenerationCard({
       console.log('[ImageGenerationCard] Making request to image generation endpoint');
       console.log('[ImageGenerationCard] Request body:', requestBody);
 
+      // fetchAPI extracts data from unified format {success: true, data: {...}}
+      // So data is the extracted response payload
       const data = await fetchAPI('/v1/system/settings/integrations/image_generation/generate/', {
         method: 'POST',
         body: JSON.stringify(requestBody),
@@ -145,8 +147,10 @@ export default function ImageGenerationCard({
 
       console.log('[ImageGenerationCard] Response data:', data);
 
-      if (!data.success) {
-        throw new Error(data.error || 'Failed to generate image');
+      // fetchAPI extracts data from unified format, so data is the response payload
+      // If fetchAPI didn't throw, the request was successful
+      if (!data || typeof data !== 'object') {
+        throw new Error('Invalid response format');
       }
 
       const imageData = {