[Backend] Add API Rate Limiting

[Abd-Standard]

Description

Protect backend services from abuse by introducing configurable request rate limits.

Tasks
Implement middleware.
Configure per-user limits.
Return meaningful error responses.
Add monitoring metrics.

Acceptance Criteria
Excessive requests are blocked.
Valid requests remain unaffected.
Rate limit events are logged.

[rahimatonize]

Hi maintainer, I'd like to take this issue. I can implement a configurable rate-limiting middleware with per-user limits, ensure proper error responses for throttled requests, and add logging/metrics so rate-limit events are observable without impacting normal request flow.please assign

[grantfox-oss]

🦊 GrantFox — @rahimatonize has been assigned to this issue as part of the Official Campaign campaign!

Next steps:

1. Open a Pull Request referencing this issue (e.g., Closes #125)
2. Your PR will be reviewed by the Core-Foundry maintainers

Good luck! Track your progress on GrantFox.

[grantfox-oss]

🎉 This issue has been marked as completed on GrantFox as part of the Official Campaign campaign!

@rahimatonize's PR #158 was approved and merged by @Abd-Standard.

🏆 @rahimatonize: You earned 35 FoxPoints for this contribution! Your current tier: Explorer (223 total points). Track your full progress on GrantFox.

👏 Great work, @rahimatonize! Keep contributing to Core-Foundry.