feat: VDS stress test harness (edge-only) and load-test results

- deploy/test/stress/: multi-IP masked handshake flood (flood.py), legit client
  during attack (legit.py), full orchestration (run-stress.sh), edge Dockerfile
  with socat stub backend and high/defense configs
- docs/research/load-test-report.md: v3 VDS loopback results (2026-08-04)
- README.md: performance table update (4k conn/s raw, 99.6% blocked in defense,
  legit clients RTT 2-6ms during attack)
- docs/testing.md: multi-IP masked stress-test procedure

deploy/test/stress/edge.Dockerfile

@@ -0,0 +1,7 @@
+FROM debian:bookworm-slim
+RUN apt-get update && apt-get install -y --no-install-recommends socat ca-certificates && rm -rf /var/lib/apt/lists/*
+COPY rampart-core /usr/local/bin/rampart-core
+COPY start.sh /start.sh
+RUN chmod +x /start.sh
+EXPOSE 25565 9090
+CMD ["/start.sh"]