feat(client): implement alknet-client crate — AlknetClient, dial methods, error type, SOCKS5 proxy

- Initialize alknet-client crate with Cargo.toml, deps, feature flags
- Implement ClientDialError enum with 5 variants (TlsConfig, Connect, Handshake, NoTransport, Proxy)
- Implement AlknetClient struct with builder methods (with_quinn, with_tcp_tls, with_iroh, with_socks5_proxy)
- Implement dial_quic — QUIC dial via quinn, producing a Connection
- Implement dial_tcp_tls — TCP+TLS dial via tokio-rustls, producing a Connection
- Implement dial_iroh — iroh dial, producing a Connection
- Implement SOCKS5 proxy support — Socks5ProxyConfig, Socks5Credentials, Socks5UdpSocket, proxy integration
- Add into_rustls_config() to TlsClientConfig in alknet-tls
- Add alknet-client to workspace members

Tasks: client/crate-init, client/error-type, client/client-core,
client/dial-quic, client/dial-tcp-tls, client/dial-iroh, client/socks5-proxy

Cargo.toml

@@ -8,6 +8,7 @@ members = [
     "crates/alknet-tls",
     "crates/alknet-tty",
     "crates/alknet-tty-local",
+    "crates/alknet-client",
 ]
 resolver = "2"