Introduce ConnTracker (atomic.Bool + WaitGroup) to track in-flight proxy
connections per sandbox. Before pausing a VM, the manager drains active
connections with a 2s grace period, preventing Go runtime corruption
inside the guest caused by stale TCP state surviving Firecracker
snapshot/restore.
Also add:
- AcquireProxyConn on Manager for atomic lookup + connection tracking
- Proxy cache (120s TTL) on CP SandboxProxyWrapper with single-query
DB lookup (GetSandboxProxyTarget) to avoid two round-trips
- Reset() on ConnTracker to re-enable connections if pause fails
- Internal ECDSA P-256 CA (WRENN_CA_CERT/WRENN_CA_KEY env vars); when absent
the system falls back to plain HTTP so dev mode works without certificates
- Host leaf cert (7-day TTL, IP SAN) issued at registration and renewed on
every JWT refresh; fingerprint + expiry stored in DB (cert_expires_at column
replaces the removed mtls_enabled flag)
- CP ephemeral client cert (24-hour TTL) via CPCertStore with atomic hot-swap;
background goroutine renews it every 12 hours without restarting the server
- Host agent uses tls.Listen + httpServer.Serve so GetCertificate callback is
respected (ListenAndServeTLS always reads cert from disk)
- Sandbox reverse proxy now uses pool.Transport() so it shares the same TLS
config as the Connect RPC clients instead of http.DefaultTransport
- Credentials file renamed host-credentials.json with cert_pem/key_pem/
ca_cert_pem fields; duplicate register/refresh response structs collapsed
to authResponse
