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/Cargo.toml

@@ -14,5 +14,13 @@ wzp-crypto = { workspace = true }
 wzp-transport = { workspace = true }
 tokio = { workspace = true }
 tracing = { workspace = true }
+tracing-subscriber = { workspace = true }
+async-trait = { workspace = true }
+bytes = { workspace = true }
+anyhow = "1"
+
+[[bin]]
+name = "wzp-client"
+path = "src/cli.rs"
 
 [dev-dependencies]