feat(ci): add deploy-uat job for UAT environment

Mirrors deploy-dev job but targets apps/overlays/uat. Both deploy-dev
and deploy-uat run in parallel after all build jobs complete.

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

.github/workflows/ci.yml

@@ -400,3 +400,64 @@ jobs:
           git add apps/overlays/dev/kustomization.yaml
           git commit -m "ci(dev): update cartsnitch, auth, receiptwitness, and api images"
           git push origin main
+
+  deploy-uat:
+    runs-on: runners-cartsnitch
+    needs: [build-and-push, build-and-push-auth, build-and-push-receiptwitness, build-and-push-api]
+    if: always() && !cancelled() && github.event_name == 'push' && github.ref == 'refs/heads/main'
+    steps:
+      - name: Generate GitHub App token
+        id: app-token
+        uses: actions/create-github-app-token@v1
+        with:
+          app-id: ${{ secrets.CARTSNITCH_APP_ID }}
+          private-key: ${{ secrets.CARTSNITCH_APP_PRIVATE_KEY }}
+          owner: ${{ github.repository_owner }}
+          repositories: infra
+
+      - name: Checkout infra repo
+        uses: actions/checkout@v4
+        with:
+          repository: cartsnitch/infra
+          token: ${{ steps.app-token.outputs.token }}
+          ref: main
+          path: infra
+
+      - name: Install kubectl
+        uses: azure/setup-kubectl@v4
+
+      - name: Install kustomize
+        uses: imranismail/setup-kustomize@v2
+
+      - name: Update frontend image tag
+        if: needs.build-and-push.result == 'success'
+        run: |
+          cd infra/apps/overlays/uat
+          kustomize edit set image ghcr.io/cartsnitch/cartsnitch:${{ needs.build-and-push.outputs.calver_tag }}
+
+      - name: Update auth image tag
+        if: needs.build-and-push-auth.result == 'success'
+        run: |
+          cd infra/apps/overlays/uat
+          kustomize edit set image ghcr.io/cartsnitch/auth:${{ needs.build-and-push-auth.outputs.calver_tag }}
+
+      - name: Update receiptwitness image tag
+        if: needs.build-and-push-receiptwitness.result == 'success'
+        run: |
+          cd infra/apps/overlays/uat
+          kustomize edit set image ghcr.io/cartsnitch/receiptwitness:${{ needs.build-and-push-receiptwitness.outputs.calver_tag }}
+
+      - name: Update api image tag
+        if: needs.build-and-push-api.result == 'success'
+        run: |
+          cd infra/apps/overlays/uat
+          kustomize edit set image ghcr.io/cartsnitch/api:${{ needs.build-and-push-api.outputs.calver_tag }}
+
+      - name: Commit and push to infra
+        run: |
+          cd infra
+          git config user.name "cartsnitch-ci[bot]"
+          git config user.email "cartsnitch-ci[bot]@users.noreply.github.com"
+          git add apps/overlays/uat/kustomization.yaml
+          git commit -m "ci(uat): update cartsnitch, auth, receiptwitness, and api images"
+          git push origin main