🛡️ Sentinel: [CRITICAL] Fix integer overflow in rate limiter refill

[google-labs-jules]

Identified and fixed integer overflow vulnerabilities in TokenBucketLimiter.

1. Multiplication Overflow: Large time gaps combined with high refill rates could cause periodsElapsed * refillTokens to overflow long, resulting in negative values. Added a check to cap tokensToAdd at capacity if the calculated periods are sufficient to fill the bucket.
2. Addition Overflow: Adding tokensToAdd to current tokens could overflow int if both were near Integer.MAX_VALUE. Changed the update logic to perform the addition as long and clamp the result using Math.min before casting back to int.

These changes prevent potential Denial of Service or logic errors where valid requests might be rejected or tokens incorrectly calculated. verified with new test cases covering these edge scenarios.

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PR created automatically by Jules for task 7994293176795885305 started by @SpaceLeam

[google-labs-jules]

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