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

crates/alknet-client/Cargo.toml

@@ -0,0 +1,31 @@
+[package]
+name = "alknet-client"
+version.workspace = true
+edition.workspace = true
+license.workspace = true
+description = "Native client dial seam — multi-transport dialer that produces Connections for protocol take-overs"
+repository.workspace = true
+
+[lib]
+name = "alknet_client"
+
+[features]
+default = []
+quinn = ["dep:quinn", "alknet-tls/quinn", "alknet-core/quinn"]
+tcp = ["dep:tokio-rustls", "alknet-tls/tcp"]
+iroh = ["dep:iroh", "alknet-core/iroh"]
+socks5 = ["dep:fast-socks5"]
+
+[dependencies]
+alknet-core = { path = "../alknet-core" }
+alknet-tls = { path = "../alknet-tls" }
+tokio = { version = "1", features = ["full"] }
+thiserror = "2"
+tracing = "0.1"
+quinn = { version = "0.11", optional = true }
+tokio-rustls = { version = "0.26", optional = true }
+iroh = { version = "1.0", optional = true, default-features = false, features = ["tls-aws-lc-rs"] }
+fast-socks5 = { version = "1", optional = true }
+rustls = "0.23"
+rustls-pki-types = "1"
+hex = "0.4"