feat(client): add relay CLI for Windows binary

lanparty-client-win now has a real command-line surface for the relay-facing
client session. It accepts the relay address, expected TLS server name, pinned
DER relay certificate, room code, virtual TAP MAC, and advertised datagram
budget, then connects through lanparty-client-core as role = client.

The binary reports the assigned peer id, room id, and effective TAP MTU from the
welcome response, then waits for Ctrl-C. TAP adapter binding and Windows route
pinning remain future slices, but the executable now exercises the real relay
control-plane path instead of the starter placeholder.

Test Plan:
- cargo fmt --check
- cargo test --workspace
- cargo clippy --workspace --all-targets -- -D warnings

Refs: PLAN.md Windows client relay connection

crates/lanparty-client-win/Cargo.toml

@@ -4,3 +4,9 @@ version.workspace = true
 edition.workspace = true
 
 [dependencies]
+anyhow.workspace = true
+clap.workspace = true
+lanparty-client-core = { path = "../lanparty-client-core" }
+lanparty-ctrl = { path = "../lanparty-ctrl" }
+lanparty-proto = { path = "../lanparty-proto" }
+tokio.workspace = true