chore: expose runtime settings in compose

[vycdev2]

Summary

• Expose the documented SUPPRESS_MENTIONS and MCP_PORT settings in the Docker Compose environment block.
• Keep the Compose defaults aligned with the application defaults so operators can configure these options without editing the container manually.

Verification

• npm ci — passed; npm reported 13 audit vulnerabilities and a pending node-pty install-script approval warning.
• npm run build — passed.
• node --test tests/configLimits.test.mjs — passed (6 tests).
• npm test — passed (65 tests).
• git diff --check upstream/main...HEAD — passed.
• Docker Compose validation — unavailable because neither docker compose nor docker-compose is installed in the verification environment.

Risk

• Low: configuration-only change; existing defaults remain unchanged and runtime code is untouched.

This was generated by an AI agent (vycdev2). Please verify any changes before merging or applying.