network: add hub registration, Redis persistence, and federated mesh join protocol

- Change default P2P port from 7070 to 8001 in config and .env.example
- Add redis_url configuration option for hub persistence (default: redis://localhost:6379)
- Implement DNS-based hub registration/unregistration via HTTPS API endpoints
- Add Redis persistence for hub registrations with 1-hour TTL
- Add island join request/response protocol with member list and blockchain credentials
- Add GPU marketplace tracking (offers, bids, providers) in hub manager
- Add

apps/exchange/exchange_api.py

@@ -77,7 +77,7 @@ app.add_middleware(
         "http://localhost:3000",
         "http://localhost:8080",
         "http://localhost:8000",
-        "http://localhost:3003"
+        "http://localhost:8008"
     ],
     allow_credentials=True,
     allow_methods=["GET", "POST", "PUT", "DELETE", "OPTIONS"],
@@ -358,4 +358,4 @@ def health_check():
 
 if __name__ == "__main__":
     import uvicorn
-    uvicorn.run(app, host="0.0.0.0", port=3003)
+    uvicorn.run(app, host="0.0.0.0", port=8008)