feat: Wino-style compact mail view with display modes + hover actions

- CompactMailDelegate: 3 display modes (Compact/Medium/Spacious) like WinUI original
  * Compact: 64px, minimal, no preview
  * Medium: 96px, with preview, detailed categories
  * Spacious: 120px, full padding, preview visible
- Hover actions: Reply (↩), Forward (↪), Mark unread (✎) on right side
- Unread dot indicator (top-right, blue) like WinUI
- User-configurable display mode via combo box in filter bar
- MainMainWindow handlers for reply/forward/mark-unread from compact view
- Signals: replyRequested, forwardRequested, markUnreadRequested

build/CMakeFiles/wino-mail-qt.dir/src/ui/delegates/CompactMailDelegate.cpp.o.d

@@ -553,4 +553,6 @@ CMakeFiles/wino-mail-qt.dir/src/ui/delegates/CompactMailDelegate.cpp.o: \
  /usr/include/x86_64-linux-gnu/qt6/QtCore/qdatetime.h \
  /usr/include/x86_64-linux-gnu/qt6/QtCore/qcalendar.h \
  /usr/include/x86_64-linux-gnu/qt6/QtCore/QDebug \
- /usr/include/x86_64-linux-gnu/qt6/QtCore/qdebug.h
+ /usr/include/x86_64-linux-gnu/qt6/QtCore/qdebug.h \
+ /usr/include/x86_64-linux-gnu/qt6/QtGui/QCursor \
+ /usr/include/x86_64-linux-gnu/qt6/QtGui/qcursor.h