docs: add proxy rate limit guidance for nodes

[unclekaldoteth]

Fixes #1762

Summary

• Add guidance for running a Stacks node behind a reverse proxy with rate limiting.
• Include Nginx and HAProxy examples for RPC (20443) and API (3999) endpoints.
• Clarify that the P2P port (20444) should not be proxied.

Changes

• docs/operate/run-a-node/run-a-node-with-docker.md
• docs/operate/readme/run-a-node-with-docker.md

Testing

npx --yes markdownlint-cli --disable MD001 MD013 MD022 MD031 -- docs/operate/run-a-node/run-a-node-with-docker.md docs/operate/readme/run-a-node-with-docker.md
echo "exit_code=$?"
# exit_code=0

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