feat: web bridge — browser-based voice calls via WebSocket

New wzp-web crate serves a web page with:
- Browser mic capture via Web Audio API (48kHz mono)
- WebSocket transport for raw PCM audio
- Server-side Opus encode/decode + FEC through wzp relay
- Real-time audio playback in browser
- Level meter and connection stats

Usage:
  wzp-relay --listen 0.0.0.0:4433    # start relay
  wzp-web --port 8080 --relay 127.0.0.1:4433  # start web bridge
  Open http://localhost:8080 in browser

Two browsers connected to the same relay get bridged for a call.

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

crates/wzp-web/Cargo.toml

@@ -0,0 +1,27 @@
+[package]
+name = "wzp-web"
+version.workspace = true
+edition.workspace = true
+license.workspace = true
+rust-version.workspace = true
+description = "WarzonePhone web bridge — browser audio via WebSocket to wzp relay"
+
+[dependencies]
+wzp-proto = { workspace = true }
+wzp-codec = { workspace = true }
+wzp-fec = { workspace = true }
+wzp-crypto = { workspace = true }
+wzp-transport = { workspace = true }
+wzp-client = { path = "../wzp-client" }
+tokio = { workspace = true }
+tracing = { workspace = true }
+tracing-subscriber = { workspace = true }
+bytes = { workspace = true }
+anyhow = "1"
+axum = { version = "0.8", features = ["ws"] }
+tower-http = { version = "0.6", features = ["fs"] }
+futures = "0.3"
+
+[[bin]]
+name = "wzp-web"
+path = "src/main.rs"