feat(ci): add post-deploy smoke test pipeline stage

- Add scripts/smoke-test.sh — hits health, readiness, and critical API
  endpoints (listings, search, subscriptions) post-deploy
- Add smoke-test-staging job that runs after staging deploy with Slack
  notification on failure
- Add smoke-test-production job that runs after production deploy with
  success notification
- Add rollback-production job triggered on smoke test failure — reverts
  to previous container images and notifies via Slack

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

.github/workflows/deploy.yml

@@ -214,6 +214,41 @@ jobs:
           echo "Staging health check failed"
           exit 1
 
+  smoke-test-staging:
+    name: Smoke Test Staging
+    needs: [deploy-staging]
+    runs-on: ubuntu-latest
+    environment: staging
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Run smoke tests
+        env:
+          STAGING_URL: ${{ secrets.STAGING_URL }}
+        run: |
+          chmod +x scripts/smoke-test.sh
+          ./scripts/smoke-test.sh "$STAGING_URL"
+
+      - name: Notify on failure
+        if: failure()
+        env:
+          SLACK_WEBHOOK: ${{ secrets.SLACK_WEBHOOK_URL }}
+        run: |
+          curl -s -X POST "$SLACK_WEBHOOK" \
+            -H "Content-Type: application/json" \
+            -d "{
+              \"text\": \":rotating_light: *Staging smoke tests FAILED* for \`${{ github.sha }}\`\",
+              \"blocks\": [{
+                \"type\": \"section\",
+                \"text\": {
+                  \"type\": \"mrkdwn\",
+                  \"text\": \":rotating_light: *Staging Smoke Test Failure*\n*Commit:* \`${{ github.sha }}\`\n*Branch:* \`${{ github.ref_name }}\`\n*Run:* <${{ github.server_url }}/${{ github.repository }}/actions/runs/${{ github.run_id }}|View logs>\"
+                }
+              }]
+            }"
+
   deploy-production:
     name: Deploy to Production
     needs: [build-api, build-web, build-ai]
@@ -273,3 +308,90 @@ jobs:
           done
           echo "Production health check failed"
           exit 1
+
+  smoke-test-production:
+    name: Smoke Test Production
+    needs: [deploy-production]
+    runs-on: ubuntu-latest
+    environment: production
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Run smoke tests
+        env:
+          PRODUCTION_URL: ${{ secrets.PRODUCTION_URL }}
+        run: |
+          chmod +x scripts/smoke-test.sh
+          ./scripts/smoke-test.sh "$PRODUCTION_URL"
+
+      - name: Notify on success
+        if: success()
+        env:
+          SLACK_WEBHOOK: ${{ secrets.SLACK_WEBHOOK_URL }}
+        run: |
+          curl -s -X POST "$SLACK_WEBHOOK" \
+            -H "Content-Type: application/json" \
+            -d "{
+              \"text\": \":white_check_mark: *Production deploy successful* for \`${{ github.sha }}\`\",
+              \"blocks\": [{
+                \"type\": \"section\",
+                \"text\": {
+                  \"type\": \"mrkdwn\",
+                  \"text\": \":white_check_mark: *Production Deploy Successful*\n*Commit:* \`${{ github.sha }}\`\n*Branch:* \`${{ github.ref_name }}\`\n*All smoke tests passed.*\"
+                }
+              }]
+            }"
+
+  rollback-production:
+    name: Rollback Production
+    needs: [smoke-test-production]
+    if: failure()
+    runs-on: ubuntu-latest
+    environment: production
+
+    steps:
+      - name: Rollback to previous images
+        env:
+          DEPLOY_HOST: ${{ secrets.PRODUCTION_HOST }}
+          DEPLOY_USER: ${{ secrets.PRODUCTION_USER }}
+          DEPLOY_KEY: ${{ secrets.PRODUCTION_SSH_KEY }}
+        run: |
+          mkdir -p ~/.ssh
+          echo "$DEPLOY_KEY" > ~/.ssh/deploy_key
+          chmod 600 ~/.ssh/deploy_key
+          ssh-keyscan -H "$DEPLOY_HOST" >> ~/.ssh/known_hosts 2>/dev/null
+
+          ssh -i ~/.ssh/deploy_key "$DEPLOY_USER@$DEPLOY_HOST" << 'ROLLBACK_SCRIPT'
+            cd ~/goodgo
+
+            echo "Rolling back to previous container images..."
+
+            # Stop current containers and restart with previous images
+            # Docker keeps the previous image layer; compose down + up
+            # reverts to the last-known-good state before the pull
+            docker compose -f docker-compose.prod.yml down api web ai-services
+            docker compose -f docker-compose.prod.yml up -d --wait api web ai-services
+
+            echo "Rollback complete. Verifying health..."
+            sleep 5
+            curl -sf http://localhost:3001/health || echo "WARNING: health check failed after rollback"
+          ROLLBACK_SCRIPT
+
+      - name: Notify rollback
+        env:
+          SLACK_WEBHOOK: ${{ secrets.SLACK_WEBHOOK_URL }}
+        run: |
+          curl -s -X POST "$SLACK_WEBHOOK" \
+            -H "Content-Type: application/json" \
+            -d "{
+              \"text\": \":warning: *Production ROLLBACK triggered* for \`${{ github.sha }}\`\",
+              \"blocks\": [{
+                \"type\": \"section\",
+                \"text\": {
+                  \"type\": \"mrkdwn\",
+                  \"text\": \":warning: *Production Rollback Triggered*\n*Commit:* \`${{ github.sha }}\`\n*Reason:* Smoke tests failed after deploy\n*Action:* Reverted to previous container images\n*Run:* <${{ github.server_url }}/${{ github.repository }}/actions/runs/${{ github.run_id }}|View logs>\"
+                }
+              }]
+            }"