fix: voice message display and playback — complete flow

- db_manager: getMessagesSince() now parses m.contentType from JSON (was missing)
- messagelist: setVoiceMessageRoles uses data directly as payload, not re-parsed as JSON
  (data is already the 'd' field value extracted by db_manager)

tools/chatgui/db/db_manager.cpp

@@ -212,6 +212,8 @@ QList<MessageRow> DbManager::getMessagesSince(const QString& chId, qint64 sinceI
         m.id           = sqlite3_column_int64(stmt, 0);
         m.authorNodeId = (quint64)sqlite3_column_int64(stmt, 1);
         QByteArray jdata = colBlob(stmt, 2);
+        m.contentType  = QString::fromUtf8(parseJsonField(jdata, "ct"));
+        if (m.contentType.isEmpty()) m.contentType = "text/plain";
         m.data         = parseJsonField(jdata, "d");
         m.timestamp    = sqlite3_column_int64(stmt, 3);
         m.datahash     = 0;