e2e: AES-128-CCM encryption via BGP router (ROUTER_FLAG_ENCRYPTED), ECDH key per peer-pair from NODEINFO pubkeys, cache 8 entries

- etcp_router.h/c: new flag ROUTER_FLAG_ENCRYPTED (0x04), etcp_route_send_encrypted(), inflight/retrans/send_q support
- utun_instance.h: e2e_ctx_cache[8] — per-peer sc_context_t cache with derived session key
- topo_node.c: topo_node_sign_self() — single point for Ed25519 self-signing of NODEINFO
- topo_node.c: fix stale x25519_self_sig after address update (topo_node_sign_self call)
- nat_detection.c: fix stale x25519_self_sig after in-place socket meta modification
- test_etcp_router_unit: 5 E2E tests (basic round-trip, no NODEINFO drop, tampered, cache reuse, ENCRYPTED+SIGNED combined)
- builds clean, 70/70 tests pass

tools/chatgui/src/memberlistmodel.cpp

@@ -35,6 +35,7 @@ QVariant MemberListModel::data(const QModelIndex& index, int role) const {
             return QString(it->online ? "online" : "offline") + " | 0x" +
                    QString("%1").arg(it->nodeId, 16, 16, QChar('0'));
         if (role == Qt::UserRole + 2) return it->isSelf;
+        if (role == Qt::UserRole + 3) return it->flags;
         return {};
     }
 
@@ -93,6 +94,7 @@ void MemberListModel::loadBatch(int from, int count) {
         item.nodeId = members[i].nodeId;
         item.isSelf = (item.nodeId == m_db->myNodeId());
         item.online = members[i].online;
+        item.flags = members[i].flags;
         QString shortId = QString("%1").arg(members[i].nodeId, 8, 16, QChar('0')).right(4).toUpper();
         item.name = members[i].name.isEmpty() ? shortId : members[i].name;
         item.localNick = members[i].localNick;