fix(ci): delete completed Jobs before Flux reconciles (GRO-481)

Both promote-to-uat and promote-prod workflows now delete any
existing completed Jobs with the same short SHA suffix before Flux
reconciles. This prevents the immutable-podTemplate error that was
blocking UAT at image tag a67e541:

  Job.batch "migrate-schema-xxx" is invalid: spec.template: field is immutable

Also added missing failure notification step to promote-prod workflow.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

.github/workflows/promote-to-uat.yml

@@ -95,6 +95,16 @@ jobs:
             --body "[GRO-429](/GRO/issues/GRO-429) — UAT promotion triggered by CTO")
           gh pr merge "$PR_URL" --merge
 
+      - name: Delete existing completed Jobs before Flux reconciles
+        env:
+          TAG: ${{ inputs.image_tag }}
+        run: |
+          SHORT_SHA="${TAG##*-}"
+          echo "Deleting completed Jobs with name suffix: $SHORT_SHA"
+          kubectl delete job "migrate-schema-${SHORT_SHA}" -n groombook-uat --ignore-not-found
+          kubectl delete job "seed-test-data-${SHORT_SHA}" -n groombook-uat --ignore-not-found
+          echo "Jobs deleted, Flux will reconcile with fresh objects"
+
       - name: Notify on failure
         if: failure()
         uses: actions/github-script@v7