chore: show compact attachment count instead of thumbnails in comment previews

When truncate mode is active (comment list), display an inline file icon
with attachment count instead of rendering full image thumbnails.

web/src/components/MemoPreview/MemoPreview.tsx

@@ -132,9 +132,17 @@ const MemoPreview = ({
         )}
       >
         {showMeta && meta}
-        {showMeta && truncate && hasContent && <div className="text-muted-foreground/50 shrink-0">·</div>}
+        {showMeta && truncate && (hasContent || hasAttachments) && <div className="text-muted-foreground/50 shrink-0">·</div>}
         {contentNode}
-        {hasAttachments && <AttachmentThumbnails attachments={attachments} />}
+        {hasAttachments &&
+          (truncate ? (
+            <div className="shrink-0 text-muted-foreground/70 inline-flex justify-center items-center gap-0.5">
+              <FileIcon className="w-3 h-3 inline-block" />
+              <span className="text-xs">{attachments.length}</span>
+            </div>
+          ) : (
+            <AttachmentThumbnails attachments={attachments} />
+          ))}
       </div>
     </MemoViewContext.Provider>
   );