feat: media_async + media_index modules, media_files table, tests

- media_async: thread-per-task async engine with primitives (sha256, sign, copy, uuid, file_size)
- media_index: media_files DB table with register_async for indexing chunks
- chat_msg: async media submission via register_async, simplified chat_msg_submit fields
- voice_recorder/attachment_sender: write single file (no chunk splitting on caller side)
- inputbar/messagelist: updated to new simplified submit interface
- test_media_async: 4-thread stress test (200K ops / 2 sec, 0 errors)
- test_media_index: 9 cases covering commit edge cases + async flow
- build: Makefile.am, CMakeLists.txt, utun_sources.cmake updated

tools/chatgui/src/messagedelegate.cpp

@@ -185,6 +185,16 @@ static int measureTextHeight(const QFont &font, const QString &text, int width)
     return r.height();
 }
 
+static QString formatFileSize(qint64 bytes) {
+    if (bytes < 1024) return QString("%1B").arg(bytes);
+    double kb = bytes / 1024.0;
+    if (kb < 1024.0) return QString("%1KB").arg(kb, 0, 'f', kb < 10.0 ? 1 : 0);
+    double mb = kb / 1024.0;
+    if (mb < 1024.0) return QString("%1MB").arg(mb, 0, 'f', mb < 10.0 ? 1 : 0);
+    double gb = mb / 1024.0;
+    return QString("%1GB").arg(gb, 0, 'f', 1);
+}
+
 static int calcMaxLineWidth(const QFont &font, const QString &text, int availW) {
     int maxW = 0;
     int pos = 0;
@@ -259,6 +269,35 @@ MessageDelegate::Layout MessageDelegate::calcLayout(
         return L;
     }
 
+    /* File attachment detection */
+    L.isFile = (contentType == "application/octet-stream");
+    if (L.isFile) {
+        QFontMetrics fm(option.font);
+        int th = fm.height();
+        int ih = 24;      /* icon height */
+        L.bubbleWidth = 230;
+        int bubbleH = kPadTop + ih + 2 + th + kPadBot;
+        L.totalHeight = qMax(bubbleH, kAvatar) + kItemGap;
+
+        int contentEdge = L.isOutgoing
+            ? L.viewWidth - (L.narrow ? kMarginH : (kMarginH + kAvatar + kGap))
+            : (L.narrow ? kMarginH : (kMarginH + kAvatar + kGap));
+        int bx = L.isOutgoing ? (contentEdge - L.bubbleWidth) : contentEdge;
+        L.bubbleRect = QRect(bx, 0, L.bubbleWidth, bubbleH);
+
+        L.textRect = QRect(bx + kPadH + ih + 8, kPadTop, L.bubbleWidth - 2*kPadH - ih - 8, th);
+        L.statusRect = QRect(bx + kPadH + ih + 8 - 48, kPadTop + th + 2, L.bubbleWidth - 2*kPadH - ih - 8 + 48 - 40, th);
+
+        if (!L.narrow) {
+            int avatarY = L.bubbleRect.bottom() - kAvatar;
+            if (!L.isOutgoing)
+                L.avatarRect = QRect(kMarginH, avatarY, kAvatar, kAvatar);
+            else
+                L.avatarRect = QRect(L.viewWidth - kMarginH - kAvatar, avatarY, kAvatar, kAvatar);
+        }
+        return L;
+    }
+
     L.emojiCount = detectEmojiOnly(text);
     L.emojiOnly = (L.emojiCount >= 1);
 
@@ -758,6 +797,46 @@ void MessageDelegate::paint(QPainter *painter, const QStyleOptionViewItem &optio
         return;
     }
 
+    if (L.isFile) {
+        drawBubble(painter, L, option);
+        if (!L.narrow) drawAvatar(painter, L, index);
+
+        /* File icon */
+        QFont iconFont = option.font;
+        iconFont.setPointSize(iconFont.pointSize() + 6);
+        painter->setFont(iconFont);
+        painter->setPen(option.palette.text().color());
+        QRect iconRect(L.bubbleRect.left() + kPadH, kPadTop, 24, 24);
+        painter->drawText(iconRect, Qt::AlignCenter, QString::fromUtf8("\xF0\x9F\x93\x84"));
+
+        QFont fileFont = option.font;
+        fileFont.setBold(true);
+        painter->setFont(fileFont);
+        painter->setPen(option.palette.text().color());
+        QString displayName = index.data(MsgFileDisplayNameRole).toString();
+        painter->drawText(L.textRect, Qt::AlignLeft | Qt::AlignVCenter, displayName);
+
+        QFont sizeFont = option.font;
+        sizeFont.setPointSize(sizeFont.pointSize() - 2);
+        painter->setFont(sizeFont);
+        painter->setPen(QColor(0x80, 0x80, 0x80));
+        qint64 fsz = index.data(MsgFileSizeRole).toLongLong();
+        QString sizeStr = formatFileSize(fsz);
+        int nameH = QFontMetrics(fileFont).height();
+        QRect sizeRect(L.textRect.left(), L.textRect.top() + nameH, L.textRect.width(), QFontMetrics(sizeFont).height());
+        painter->drawText(sizeRect, Qt::AlignLeft | Qt::AlignVCenter, sizeStr);
+
+        /* Timestamp */
+        QFont tsFont = option.font;
+        tsFont.setPointSize(tsFont.pointSize() - 1);
+        painter->setFont(tsFont);
+        painter->drawText(QRect(L.textRect.right() - 40, L.textRect.top() + nameH, 40, QFontMetrics(sizeFont).height()),
+                          Qt::AlignRight | Qt::AlignVCenter, index.data(MsgTimeRole).toString());
+
+        painter->restore();
+        return;
+    }
+
     auto *cv = qobject_cast<const ChatView *>(option.widget);
     bool singleTextSel = false;
     bool multiRowSel   = false;