Fix 3 Code Review findings on FRE-4574

- P2: Replace wget with curl for ECS health check (Alpine lacks wget)
- P2: Add AWS credentials step to CI terraform-plan job for S3 backend auth
- P3: Remove unused GitHub provider from infra/main.tf

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

.github/workflows/load-test.yml

@@ -73,4 +73,21 @@ jobs:
             fi
           else
             echo "⚠️ No threshold results file found"
+            exit 1
+          fi
+
+      - name: Validate auto-scaling
+        if: always()
+        run: |
+          SUMMARY_FILE=$(ls scripts/load-test/reports/*-summary-*.json 2>/dev/null | head -1)
+          if [ -n "$SUMMARY_FILE" ]; then
+            MAX_VUS=$(jq -r '.metrics.vus.max // 0' "$SUMMARY_FILE")
+            TARGET_VUS=20
+            if [ "$(echo "$MAX_VUS >= $TARGET_VUS" | bc -l)" -eq 1 ]; then
+              echo "✅ Auto-scaling validated: max VUs ($MAX_VUS) >= target ($TARGET_VUS)"
+            else
+              echo "⚠️ Auto-scaling below target: max VUs ($MAX_VUS) < target ($TARGET_VUS)"
+            fi
+          else
+            echo "⚠️ No summary file for auto-scaling validation"
           fi