v0.4.0 - Release

Multi-file transfer support + connectivity improvements

• NEW: Multi-file transfer within single session for both transfer modes (UDP and TCP relay). Transfer a directory recursively, mirroring source file/folder structure at destination
• NEW: Protocol - New message codes for file offers, acceptance, rejections
• NEW: Skip files when source/dest files are identical (filesize + SHA)
• NEW: With conflicts, ask user or use parameters (overwrite, skip, keep both, ask=default)
• IMPROVE: Reconnect: best effort if line dropped, reuse same port to attempt re-pair with peers
• IMPROVE: Peers report LAN endpoint (so same-NAT peers can skip punch and connect via LAN)
• IMPROVE: Resume interrupted file transfer from last checkpoint (use sidecar files)
• NEW: CLI parameters to force TCP relay, set Max Reconnect attempts, budget for folder transfer
• NEW: Added tests and scripts to validate folder transfer functionality