Security: Atomic Rate Limiting & Concurrency Fix

[MichaelSovereign]

Summary

This PR fixes a critical race condition in the IP-based rate limiting logic that could allow attackers to bypass miner registration limits.

Changes

1. Atomic Transactions: Wrapped the rate limit check in to ensure that multiple concurrent worker processes (e.g., under Gunicorn) cannot increment the counter beyond the allowed limit before the DB write is committed.
2. Robust Error Handling: Added explicit rollback and error handling to prevent database locks or corruption during high-concurrency attestation floods.
3. Improved Accuracy: Ensures that failed attempts do not incorrectly count towards the IP's limit.

Closes #7423