ws_transport implementation over an HTTP/3 (QUIC) stream.

After an extended-CONNECT WebSocket handshake (RFC 9220), the WS session exchanges frames as HTTP/3 DATA on the same stream. This module maps the ws_transport callbacks onto the quic_h3 library:

• send/2 -> quic_h3:send_data/4
• controlling_process/2 -> quic_h3:set_stream_handler/4
• classify/2 turns {quic_h3, Conn, {data, ...}} into {ws_data, ...} and resets into {ws_error, ...}

The handle is {Conn, StreamId}.