Silo Apk

feat: switch file transfer to TCP for reliable large-file support

File payloads previously went over UDP in 60 KB chunks, each of which was
IP-fragmented into ~42 fragments; a single lost fragment dropped the whole
chunk, so transfers failed once files grew past a few KB.

Add a TCP file channel: a ServerSocket on port 41238 receives inbound files
(runTcpServer/handleTcpClient) and sendFileTCP streams outbound files to the
desktop's TCP port. UDP is kept for discovery, pairing, control, and frames.
Update README to reflect the hybrid UDP/TCP transport.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>