feat: expose DHT lifecycle and lookup APIs

[Yu-da-1]

Hi, this is my first time writing code in Haskell, so please let me know if there are any issues. Thank you for the opportunity to contribute to this project!

Summary

Adds high-level getValue and findPeer wrappers over the existing iterative DHT lookups, and exposes DHT lifecycle and operations through the LibP2P public facade. No lookup or wire behavior is changed.

Spec reference

No protocol behavior change.

Testing

• Added API tests for retrieving a record stored through putValue
• Added API coverage for finding the closest known peers
• Built the complete test suite successfully
• Ran 1271 examples with 0 failures
• Manually verified that a DHT workflow type-checks using only import LibP2P

Closes #285

[adust09]

Thank you so much for your effor!

No blocking findings. The new wrappers remain thin aliases over the existing iterative lookups, and the facade exports are sufficient for a DHT lifecycle/workflow using only import LibP2P.

Approved