feat(agentnetwork): thread the zone config through to the manager

Adds AgentNetwork.Zone to the management config and passes it to the
agent-network manager, alongside the existing plumbing in the combined
binary. Nothing reads it yet -- the allocator that stamps it onto new rows
comes next -- so this commit is inert on its own.

management/internals/server/modules.go

@@ -202,6 +202,7 @@ func (s *BaseServer) AgentNetworkManager() agentnetwork.Manager {
 			s.PermissionsManager(),
 			s.AccountManager(),
 			s.ServiceProxyController(),
+			s.Config.AgentNetworkZone,
 		)
 		// Sweep expired agent-network access logs per account retention,
 		// reusing the reverse-proxy cleanup interval config.