feat(ci): simplify golden image name format to com-ermnvldmr-debian-12-k3s-amd64-<short_sha>.qcow2 (#30)

### Summary of Changes

- Simplified golden image naming to:
`com-ermnvldmr-debian-12-k3s-amd64-<short_sha>.qcow2` without timestamps
or `sha-` prefix.

.github/workflows/ci-next-build-golden-image.yml

@@ -34,9 +34,8 @@ jobs:
       - name: Calculate Image Name
         id: vars
         run: |
-          TIMESTAMP="$(date -u +'%Y-%m-%d-%H-%M-%S')"
-          SHORT_SHA="sha-$(echo ${{ github.sha }} | cut -c1-7)"
-          IMAGE_NAME="com-ermnvldmr-debian-12-k3s-amd64-${TIMESTAMP}-${SHORT_SHA}.qcow2"
+          SHORT_SHA="$(echo ${{ github.sha }} | cut -c1-7)"
+          IMAGE_NAME="com-ermnvldmr-debian-12-k3s-amd64-${SHORT_SHA}.qcow2"
           echo "image_name=${IMAGE_NAME}" >> "$GITHUB_OUTPUT"
 
       - name: Install Build Tools