Update in-memory rate limiter to fail secure (reject new requests) when maximum capacity is reached, rather than evicting the oldest tracking entry. This prevents an attacker from bypassing their rate limit by flooding the store with spoofed `x-forwarded-for` IPs to intentionally trigger cache eviction. Also cleaned up temporary files and updated tests to verify the behavior.
Co-authored-by: google-labs-jules[bot] <161369871+google-labs-jules[bot]@users.noreply.github.com>
