[BenCodez]

Summary

Extract registered reward state and lookup/update behavior from RewardHandler into RewardRegistry under com.bencodez.advancedcore.api.rewards.

Changes

• add api.rewards.RewardRegistry
• move ownership of loaded rewards, directly-defined rewards, and sub-directly-defined rewards into the registry
• move reward lookup, direct/sub-direct lookup, duplicate detection, reward existence checks, and registered reward replacement into the registry
• keep RewardHandler as the public compatibility facade and preserve its existing getter/method signatures
• keep reward loading, execution, built-in inject registration, validation, and sub-reward discovery orchestration in RewardHandler for later focused refactors
• preserve existing lookup semantics, including current case-sensitivity/case-insensitivity behavior
• add RewardRegistryTest characterization coverage

This is intended as a behavior-preserving refactor with no reward config changes.