[client] Apply the published upload destination at login too

Engine.Start receives the login response's NetbirdConfig but only runs it
through PopulateNetbirdConfig, so handleDebugUploadUpdate never saw it: the
destination the management server publishes reached the engine only on the
first sync afterwards. A debug bundle requested in that window resolved no
published destination and fell back to the service NetBird runs, even on a
deployment that had configured its own — the opposite of what configuring it
is for.

Seen with a remote job triggered shortly after the peer reconnected: the job
succeeded against NetBird's upload service while the account setting named a
different host.

client/internal/engine.go

@@ -615,6 +615,13 @@ func (e *Engine) Start(netbirdConfig *mgmProto.NetbirdConfig, mgmtURL *url.URL)
 		log.Warnf("failed to populate DNS cache: %v", err)
 	}
 
+	// The login response carries the same NetbirdConfig a sync does, but Start
+	// does not run it through updateNetbirdConfig. Without this, a bundle
+	// requested between login and the first sync sees no published destination
+	// and falls back to the service NetBird runs, even where the deployment
+	// configured its own.
+	e.handleDebugUploadUpdate(netbirdConfig.GetDebug())
+
 	e.routeManager = routemanager.NewManager(routemanager.ManagerConfig{
 		Context:             e.ctx,
 		PublicKey:           e.config.WgPrivateKey.PublicKey().String(),