fix CI deploy: align image var name (BE_IMAGE → IMAGE)

k8s/backend.yaml referenced ${BE_IMAGE} but the workflow env
defines ${IMAGE}, causing envsubst to produce an empty image
name (InvalidImageName). Also consolidated the summary table
to single image line since FE/BE are merged.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.gitea/workflows/ci.yaml

@@ -773,8 +773,7 @@ jobs:
           echo "| | |" >> $GITHUB_STEP_SUMMARY
           echo "|---|---|" >> $GITHUB_STEP_SUMMARY
           echo "| **URL** | https://${HOST}${BP}/ |" >> $GITHUB_STEP_SUMMARY
-          echo "| **Backend** | \`${BE_IMAGE}:${{ steps.setup.outputs.IMAGE_TAG }}\` |" >> $GITHUB_STEP_SUMMARY
-          echo "| **Frontend** | \`${FE_IMAGE}:${{ steps.setup.outputs.IMAGE_TAG }}\` |" >> $GITHUB_STEP_SUMMARY
+          echo "| **Image** | \`${IMAGE}:${{ steps.setup.outputs.IMAGE_TAG }}\` |" >> $GITHUB_STEP_SUMMARY
           echo "| **Database** | \`${{ steps.setup.outputs.DB_NAME }}\` |" >> $GITHUB_STEP_SUMMARY
           echo "| **DB Wipe** | ${{ steps.setup.outputs.DB_WIPE }} |" >> $GITHUB_STEP_SUMMARY
           if [[ -n "${{ vars.STORAGE_CLASS }}" ]]; then