Move RateLimiter, ProgressiveRateLimiter, and cleanup functions to ratelimit_shared.go. Add dev and prod rate limiter tests. Remove inline cleanup goroutines. Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent) Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>