feat: Phase 2 — relay daemon and client library with integration pipelines

wzp-relay:
- RelayPipeline: ingest → FEC decode → jitter buffer → FEC encode → send
- SessionManager: tracks active calls, idle expiry
- RelayConfig: TOML-based configuration
- Binary: accepts QUIC connections, receives media packets

wzp-client:
- CallEncoder: mic PCM → Opus encode → FEC → MediaPackets
- CallDecoder: MediaPackets → FEC decode → jitter → Opus decode → PCM
- CLI binary: connects to relay, sends test silence frames

99 tests passing across all 7 crates.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

crates/wzp-client/src/cli.rs

@@ -0,0 +1,56 @@
+//! WarzonePhone CLI test client.
+//!
+//! Usage: wzp-client <relay-addr>
+//!
+//! Connects to a relay and sends silence frames for testing.
+
+use std::net::SocketAddr;
+
+use tracing::{error, info};
+
+use wzp_client::call::{CallConfig, CallEncoder};
+use wzp_proto::MediaTransport;
+
+#[tokio::main]
+async fn main() -> anyhow::Result<()> {
+    tracing_subscriber::fmt().init();
+
+    let relay_addr: SocketAddr = std::env::args()
+        .nth(1)
+        .unwrap_or_else(|| "127.0.0.1:4433".to_string())
+        .parse()?;
+
+    info!(%relay_addr, "WarzonePhone client connecting");
+
+    let client_config = wzp_transport::client_config();
+    let endpoint = wzp_transport::create_endpoint("0.0.0.0:0".parse()?, None)?;
+    let connection =
+        wzp_transport::connect(&endpoint, relay_addr, "localhost", client_config).await?;
+
+    info!("Connected to relay");
+
+    let transport = wzp_transport::QuinnTransport::new(connection);
+    let config = CallConfig::default();
+    let mut encoder = CallEncoder::new(&config);
+
+    let frame_duration = tokio::time::Duration::from_millis(20);
+    let pcm = vec![0i16; 960]; // 20ms @ 48kHz silence
+
+    for i in 0..250u32 {
+        let packets = encoder.encode_frame(&pcm)?;
+        for pkt in &packets {
+            if let Err(e) = transport.send_media(pkt).await {
+                error!("send error: {e}");
+                break;
+            }
+        }
+        if i % 50 == 0 {
+            info!(frame = i, packets = packets.len(), "sent");
+        }
+        tokio::time::sleep(frame_duration).await;
+    }
+
+    info!("Done, closing");
+    transport.close().await?;
+    Ok(())
+}