chatgui: local nicknames per channel member — edit via MemberPropsDialog, override display everywhere

tools/chatgui/db/db_manager.h

@@ -49,6 +49,7 @@ struct ChannelMember {
     quint64 nodeId = 0;
     bool    online = false;
     QString name;       // from nodes.name, empty if not set
+    QString localNick;  // from peers.local_nick override, empty if not set
 };
 
 struct NodeAddr {
@@ -96,6 +97,7 @@ public:
     QList<ChannelMember> getChannelMembers(const QString& chId, int offset, int limit) const;
     void cleanOrphanedPeers(const QString& chId) const;
     QString getDisplayName(quint64 nodeId) const;
+    QMap<quint64, QString> getLocalNicknames(const QString& chId) const;
 
     /* ── Узлы ── */
     QByteArray loadNodeInfo(quint64 nodeId) const;