- Add GeoRouter struct with regions map, defaultReg, and mutex fields
- Add Region struct with ID, Name, Endpoints, Priority, IsActive, and Latency fields
- Add GeoRoutingConfig with DefaultRegion and Regions fields
- Add NewGeoRouter constructor with region initialization
- Add GetRegionForIP method with IP parsing and geo lookup
- Add lookupRegion helper with simplified IP range-based region detection
- Add CircuitState type with StateClosed, StateOpen, and StateHalfOpen constants and String method
- Add CircuitBreaker struct with name, state, failureCount, successCount, lastFailure, config, mutex, and onStateChange fields
- Add CircuitBreakerConfig with FailureThreshold, SuccessThreshold, Timeout, and HalfOpenMaxCalls fields
- Add NewCircuitBreaker constructor and DefaultCircuitBreakerConfig with
- Add Cache struct with entries map, mutex, maxSize, defaultTTL, strategy, and stats fields
- Add CacheStrategy type with LRU, TTL, write-through, write-back, and read-through constants
- Add CacheEntry struct with Key, Value, ExpiresAt, CreatedAt, and HitCount fields
- Add NewCache constructor with CacheConfig parameter and automatic cleanup goroutine
- Add Get, Set, Delete, and Clear methods with hit
nutcas3