Add docs for rate limiting configuration and default thresholds

[Chucks1093]

Summary
The rate limiting middleware is in place but the configuration options and default thresholds are not documented. Contributors adjusting rate limits or adding new endpoints need to understand the defaults to avoid accidentally bypassing or over-restricting them.

Scope

• document the rate limiting configuration options and their default values
• note which endpoints have custom thresholds and why
• describe the response behavior when a rate limit is exceeded

Acceptance Criteria

• default thresholds are documented with their units
• custom per-endpoint thresholds are listed
• the rate-exceeded response behavior is described

Contributor coordination: if you pick this up, reach out in Telegram for updates or clarification: https://t.me/accesslayerorg

[jotel-dev]

@jotel-dev has applied to work on this issue as part of the Stellar Wave Program's 5th wave.

Pls assign me

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Congratulations, @jotel-dev! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on June 2, 2026.

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[drips-wave]

This issue has been completed by @jotel-dev as part of the Stellar Wave Program's 5th Wave 🥳

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