- Add CachedDatabase struct wrapping Database with cache.Cache field and NewCachedDatabase constructor
- Add CachedFind method with cache key generation from query/args, cache hit deserialization, database fallback on miss, and 5-minute TTL
- Add CachedFirst method with same caching pattern as CachedFind for single record queries
- Add InvalidateCache method for clearing all cache entries and InvalidateCacheKey
