fix(peers): keep TCP hole-punched connections alive with 1s pings (#2632)

Disable ping interval backoff for TCP hole-punched connections so idle
connections continue to send keepalive traffic every second. Preserve
the existing backoff and loss handling for other connections.

Keep randomized backoff above zero and cover the one-second schedule
and the existing backoff and loss retry behavior with tests.

* refactor(peers): model connection origins at admission

Record manual, direct, listener, TCP/UDP hole-punch, and attached
origins when constructing peer connections. Derive hole-punch state
from this origin instead of maintaining separate mutable flags.

Choose the one-second TCP hole-punch ping limit in PeerConn and pass
only a maximum interval to the pinger. Keep other origins on the
existing backoff schedule without inspecting tunnel type strings.

Keep origin selection internal and preserve the dedicated attached
admission paths. Update public admission callers and cover origin
propagation, relay restrictions, and ping interval limits.

easytier-web/src/central_network/gateway.rs

@@ -379,7 +379,7 @@ impl NetworkInstanceManager {
         tokio::select! {
             biased;
             _ = retiring.cancelled() => None,
-            result = peer_manager.add_tunnel_as_server(tunnel, true) => Some(result),
+            result = peer_manager.add_tunnel_as_server(tunnel) => Some(result),
         }
     }