fix: force-close user connections on removal, fix UDP upload/download counters, use self-hosted releases

- service.go: call CloseUserConnections() before RemoveUsers() so banned/reset
  users are disconnected immediately instead of waiting for natural timeout
  (upstream issue #32, PR pending 4+ months)

- conntracker.go: swap UnwrapPacketReader/Writer upload/download counters for
  UDP PacketConn path — Reader=upload, Writer=download to match TCP path
  (upstream issue #55)

- xbctl/main.go: change downloadBase to JP01 Gitea so xbctl upgrade pulls
  self-hosted patched releases instead of upstream

internal/service/service.go

@@ -838,6 +838,18 @@ func (s *Service) applyUserDelta(ctx context.Context, action string, deltaUsers
 			return
 		}
 
+		// Force-close active connections for removed users before revoking
+		// credentials. Without this, existing long-lived connections
+		// (QUIC/TCP) persist until natural timeout — subscription resets
+		// and bans would not take immediate effect.
+		if s.kernel.Capabilities().ForceCloseUser {
+			for _, u := range deltaUsers {
+				if err := s.kernel.CloseUserConnections(ctx, u.UUID); err != nil {
+					nlog.Core().Debug(fmt.Sprintf("CloseUserConnections(%s): %v", u.UUID, err))
+				}
+			}
+		}
+
 		prevUsers, prevHash := s.prepareUserState(filtered)
 		removed, err := s.kernel.RemoveUsers(deltaUsers)
 		if err != nil {