Add tests covering server security middleware

[stevenschling13]

Summary

• add Vitest coverage for Fastify security headers
• verify in-memory rate limiting enforces 429 after 100 requests
• ensure trusted callers with bypass token skip the limiter

Testing

• ./node_modules/.bin/vitest run

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https://chatgpt.com/codex/tasks/task_e_6907b6862f4c832cb68a77f8bd140362

[Copilot]

Pull Request Overview

This PR adds security-focused integration tests for the Fastify server, validating security headers and rate limiting functionality. These tests ensure that the recently added security features work correctly.

• Adds tests for security header application on responses
• Adds tests for rate limiting behavior (100 requests/minute limit)
• Adds tests for rate limit bypass token functionality