add error logging to all silent returns in chat_sync invite/join chain + GUI self-invite check

tools/chatgui/src/invitedialog.cpp

@@ -151,6 +151,39 @@ void InviteDialog::onSendInvite() {
     }
 
     uint64_t targetNodeId = sc_derive_node_id_from_pubkey((const uint8_t*)d.pubkey.constData());
+
+    /* diagnostic: show decoded link info */
+    {
+        uint64_t myNodeId = m_node ? m_node->nodeIdHex().toULongLong(nullptr, 16) : 0;
+        QString pkHex = QString::fromLatin1(d.pubkey.toHex());
+        QString pkShort = pkHex.left(8) + ".." + pkHex.right(4);
+        QString addrInfo;
+        for (int i = 0; i < d.addrs.size() && i < 3; i++) {
+            if (i > 0) addrInfo += ", ";
+            uint32_t ip4 = 0;
+            if (d.addrs[i].family == 4 && d.addrs[i].address.size() >= 4) {
+                memcpy(&ip4, d.addrs[i].address.constData(), 4);
+                addrInfo += QString("%1.%2.%3.%4:%5")
+                    .arg((ip4>>24)&0xFF).arg((ip4>>16)&0xFF).arg((ip4>>8)&0xFF).arg(ip4&0xFF)
+                    .arg(d.addrs[i].port);
+            } else {
+                addrInfo += QString("v%1:%2").arg(d.addrs[i].family).arg(d.addrs[i].port);
+            }
+        }
+        if (d.addrs.size() > 3) addrInfo += QString(" +%1 more").arg(d.addrs.size() - 3);
+        QString diag = QString("Ссылка: узел 0x%1 ключ %2, %3 адр. (%4)")
+            .arg(targetNodeId, 16, 16, QChar('0'))
+            .arg(pkShort)
+            .arg(d.addrs.size())
+            .arg(addrInfo);
+        GUI_INFO("invite_by_link: %s", diag.toUtf8().constData());
+        if (myNodeId != 0 && myNodeId == targetNodeId) {
+            GUI_WARN("invite_by_link: self-invite rejected — link contains own pubkey, node=0x%016llx", (unsigned long long)myNodeId);
+            setInviteStatus("Ошибка: это ваша собственная ссылка (нельзя пригласить себя)", true);
+            return;
+        }
+        setInviteStatus(diag);
+    }
     m_inviteSending = true;
     m_inviteTargetNodeId = targetNodeId;
     m_inviteSendBtn->setEnabled(false);