feat: 3 web client variants — Pure JS, Hybrid (JS+WASM FEC), Full WASM

Variant 1: Pure JS (wzp-pure.js)
- WebSocket transport, raw PCM, no encryption (bridge handles QUIC crypto)
- ~20KB, works everywhere, zero dependencies
- WZPPureClient class with connect/disconnect/sendAudio

Variant 2: Hybrid (wzp-hybrid.js + wzp-wasm)
- WebSocket transport + RaptorQ FEC via WASM
- ~120KB (337KB WASM blob shared with full variant)
- WZPHybridClient extends pure with FEC encode/decode
- Loss recovery ready for when WebTransport replaces WebSocket

Variant 3: Full WASM (wzp-full.js + wzp-wasm)
- WebTransport datagrams (unreliable, low latency)
- ChaCha20-Poly1305 encryption + RaptorQ FEC, all in WASM
- X25519 key exchange over bidirectional stream
- WZPFullClient — true E2E encrypted WZP client in browser
- Needs relay HTTP/3 support (h3-quinn) for WebTransport

Shared infrastructure:
- wzp-core.js: UI logic, AudioWorklet, variant detection, PTT
- audio-processor.js: AudioWorklet capture + playback (unchanged)
- index.html: variant selector (?variant=pure|hybrid|full), auto-detect

wzp-wasm crate (new):
- RaptorQ FEC encoder/decoder (WzpFecEncoder, WzpFecDecoder)
- ChaCha20-Poly1305 crypto (WzpCryptoSession)
- X25519 key exchange (WzpKeyExchange)
- 7 native tests (3 FEC + 4 crypto), all passing
- WASM blob: 337KB optimized

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

crates/wzp-wasm/Cargo.toml

@@ -0,0 +1,25 @@
+[package]
+name = "wzp-wasm"
+version = "0.1.0"
+edition = "2021"
+description = "WarzonePhone WASM bindings — FEC (RaptorQ) + crypto (ChaCha20-Poly1305, X25519)"
+
+[lib]
+crate-type = ["cdylib", "rlib"]
+
+[dependencies]
+wasm-bindgen = "0.2"
+raptorq = "2"
+js-sys = "0.3"
+
+# Crypto (ChaCha20-Poly1305 + X25519 key exchange)
+chacha20poly1305 = "0.10"
+hkdf = "0.12"
+sha2 = "0.10"
+x25519-dalek = { version = "2", features = ["static_secrets"] }
+rand = "0.8"
+getrandom = { version = "0.2", features = ["js"] }  # CRITICAL for WASM randomness
+
+[profile.release]
+opt-level = "s"
+lto = true