Disable SHA tags with branch prefix for PR builds

Co-authored-by: PhantomDave <34485699+PhantomDave@users.noreply.github.com>

Author: Copilot

.github/workflows/build-backend-image.yml

@@ -49,7 +49,7 @@ jobs:
         with:
           images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
           tags: |
-            type=sha,prefix={{branch}}-
+            type=sha,prefix={{branch}}-,enable=${{ github.event_name != 'pull_request' }}
             type=ref,event=branch
             type=ref,event=pr
             type=raw,value=latest,enable={{is_default_branch}}

.github/workflows/build-frontend-image.yml

@@ -96,7 +96,7 @@ jobs:
         with:
           images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
           tags: |
-            type=sha,prefix={{branch}}-
+            type=sha,prefix={{branch}}-,enable=${{ github.event_name != 'pull_request' }}
             type=ref,event=branch
             type=ref,event=pr
             type=raw,value=latest,enable={{is_default_branch}}