feat: Phase 9.1–9.5 — WebRTC DataChannel transport for browser P2P

Browser clients can now connect P2P to nodes behind residential NAT via
WebRTC DataChannel with ICE/STUN. Validated on SFR Port-Restricted Cone
NAT + 4G CGNAT across three scenarios (WiFi LAN, 4G IPv6, 4G IPv4 STUN).
No TURN relay needed. Hub serves only as signaling relay (<1 KB).

New files:
- webrtc_server.py: aiortc-based WebRTC transport (node side)
- signaling.py: SDP/ICE relay endpoint (hub side)
- transport.js: browser WebRTC client with msgpack framing
- webrtc-test.html: spike test page for browser→NAT→node validation
- test_webrtc_transport.py: 4 tests (handshake, file transfer, auth, guard)
- meshbay-draft-v4.md: architecture spec updated for web client

Modified:
- hub_client.py: WebRTC offer handling via hub WebSocket
- revocation.py: node_id from WS auth + webrtc_answer routing
- pyproject.toml: aiortc>=1.9 dependency

123 tests passing (117 existing + 6 new).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

1 files changed, 15 insertions, 0 deletions

diff --git a/packages/meshbay-hub/src/meshbay_hub/api/webapp.py b/packages/meshbay-hub/src/meshbay_hub/api/webapp.py
index 3d5e78b..6005927 100644
--- a/packages/meshbay-hub/src/meshbay_hub/api/webapp.py
+++ b/packages/meshbay-hub/src/meshbay_hub/api/webapp.py
@@ -27,6 +27,21 @@ async def app_js():
     return FileResponse(STATIC_DIR / "app.js", media_type="application/javascript")
 
 
+@router.get("/transport.js")
+async def transport_js():
+    return FileResponse(STATIC_DIR / "transport.js", media_type="application/javascript")
+
+
+@router.get("/crypto.js")
+async def crypto_js():
+    return FileResponse(STATIC_DIR / "crypto.js", media_type="application/javascript")
+
+
+@router.get("/webrtc-test.html")
+async def webrtc_test():
+    return FileResponse(STATIC_DIR / "webrtc-test.html", media_type="text/html")
+
+
 @router.get("/", response_class=HTMLResponse)
 async def index():
     return HTMLResponse(_HTML)