Fix docker-build-test: Load image into local Docker daemon

ISSUE:
======
- Docker build succeeds but test fails
- Error: Unable to find image 'pote:test' locally
- Image built in buildx builder but not loaded into local daemon
- docker run can't find the image to test

FIX:
====
- Added load: true to docker/build-push-action
- Loads image into local Docker daemon after build
- Allows docker run to test the image

CHANGES:
========
- docker-build-test job: Added load: true to build-push-action
- Image is now available in local daemon for testing

This ensures the Docker image can be tested after building.

.github/workflows/ci.yml

@@ -420,6 +420,7 @@ jobs:
         with:
           context: .
           push: false
+          load: true
           tags: pote:test
           cache-from: type=gha
           cache-to: type=gha,mode=max