desktop messagelist: decode *<b64> prefix for media message display

setVoiceMessageRoles now checks for '*' marker, translates URL-safe
base64 (-_ → +/) and decodes to restore original display data.
Fixes attachment filenames and voice waveform for new messages.

tools/chatgui/src/messagelist.cpp

@@ -93,6 +93,16 @@ static QString contentTypeFromJson(const QByteArray& data) {
 static void setVoiceMessageRoles(QStandardItem* item, const QByteArray& data,
                                    const QString& contentType, const QString& mediaDirBase,
                                    const QString& channelId, const QByteArray& localAttrs) {
+    QByteArray body = data;
+    if (body.startsWith('*')) {
+        int pipePos = body.indexOf('|');
+        if (pipePos > 1) {
+            QByteArray b64 = body.mid(1, pipePos - 1);
+            b64.replace('-', '+');
+            b64.replace('_', '/');
+            body = QByteArray::fromBase64(b64) + body.mid(pipePos);
+        }
+    }
     QString ct = contentType;
     if (ct.isEmpty()) ct = contentTypeFromJson(data);
     if (ct.isEmpty()) ct = "text/plain";
@@ -100,7 +110,7 @@ static void setVoiceMessageRoles(QStandardItem* item, const QByteArray& data,
     item->setData(channelId, MsgChannelIdRole);
 
     if (ct == "audio/opus") {
-        QString raw = QString::fromUtf8(data);
+        QString raw = QString::fromUtf8(body);
         if (raw.startsWith('{')) return;
 
         /* unified format: wf={base64};dur={ms};|{file_size}|{block_size}|{num_blocks}|{sigs} */
@@ -161,7 +171,7 @@ static void setVoiceMessageRoles(QStandardItem* item, const QByteArray& data,
         }
     }
     if (ct == "application/octet-stream") {
-        QString raw = QString::fromUtf8(data);
+        QString raw = QString::fromUtf8(body);
         int pipePos = raw.indexOf('|');
         QString fname = (pipePos > 0) ? raw.left(pipePos) : raw;
         item->setData(fname, MsgFileDisplayNameRole);