fix(kokoros): add missing upscale_image stub to Backend trait impl (#11414)

* Initial plan

* fix(kokoros): add missing upscale_image stub to Backend impl

Co-authored-by: mudler <2420543+mudler@users.noreply.github.com>

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: mudler <2420543+mudler@users.noreply.github.com>

backend/rust/kokoros/src/service.rs

@@ -320,6 +320,13 @@ impl Backend for KokorosService {
         Err(Status::unimplemented("Not supported"))
     }
 
+    async fn upscale_image(
+        &self,
+        _: Request<backend::UpscaleImageRequest>,
+    ) -> Result<Response<backend::Result>, Status> {
+        Err(Status::unimplemented("Not supported"))
+    }
+
     async fn generate_image(
         &self,
         _: Request<backend::GenerateImageRequest>,