feat: Pagination/virtualization (fetchMore) for EmailListModel

- EmailListModel: QAbstractListModel with canFetchMore/fetchMore
  * Batch loading (default 50 emails per fetch)
  * Total count query for scrollbar
  * TotalCountChanged signal
  * Paginated DB queries: findAllPaginated, findByFolderIdPaginated
  * Count queries: countAll, countByFolderId

- MailItemDao: new paginated methods
  * findAllPaginated(offset, limit, filters...)
  * findByFolderIdPaginated(folderId, offset, limit, filters...)
  * countAll(filters...), countByFolderId(folderId, filters...)

- MailListView: scroll-triggered fetchMore
  * Connects verticalScrollBar valueChanged on both TreeView and ListView
  * Triggers fetchMore at 90% scroll threshold
  * onRowsInserted updates EmailTreeModel when new emails arrive
  * Works in both normal (tree) and compact (list) views

build/CMakeFiles/wino-mail-qt.dir/compiler_depend.internal

@@ -28587,6 +28587,7 @@ CMakeFiles/wino-mail-qt.dir/src/ui/maillistview.cpp.o
  /usr/include/x86_64-linux-gnu/qt6/QtWidgets/QLineEdit
  /usr/include/x86_64-linux-gnu/qt6/QtWidgets/QListView
  /usr/include/x86_64-linux-gnu/qt6/QtWidgets/QPushButton
+ /usr/include/x86_64-linux-gnu/qt6/QtWidgets/QScrollBar
  /usr/include/x86_64-linux-gnu/qt6/QtWidgets/QStackedWidget
  /usr/include/x86_64-linux-gnu/qt6/QtWidgets/QStyle
  /usr/include/x86_64-linux-gnu/qt6/QtWidgets/QStyleOptionViewItem
@@ -28614,6 +28615,7 @@ CMakeFiles/wino-mail-qt.dir/src/ui/maillistview.cpp.o
  /usr/include/x86_64-linux-gnu/qt6/QtWidgets/qlistview.h
  /usr/include/x86_64-linux-gnu/qt6/QtWidgets/qpushbutton.h
  /usr/include/x86_64-linux-gnu/qt6/QtWidgets/qrubberband.h
+ /usr/include/x86_64-linux-gnu/qt6/QtWidgets/qscrollbar.h
  /usr/include/x86_64-linux-gnu/qt6/QtWidgets/qsizepolicy.h
  /usr/include/x86_64-linux-gnu/qt6/QtWidgets/qslider.h
  /usr/include/x86_64-linux-gnu/qt6/QtWidgets/qstackedwidget.h

build/CMakeFiles/wino-mail-qt.dir/compiler_depend.make

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   /usr/include/x86_64-linux-gnu/qt6/QtWidgets/QLineEdit \
   /usr/include/x86_64-linux-gnu/qt6/QtWidgets/QListView \
   /usr/include/x86_64-linux-gnu/qt6/QtWidgets/QPushButton \
+  /usr/include/x86_64-linux-gnu/qt6/QtWidgets/QScrollBar \
   /usr/include/x86_64-linux-gnu/qt6/QtWidgets/QStackedWidget \
   /usr/include/x86_64-linux-gnu/qt6/QtWidgets/QStyle \
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@@ -28564,6 +28565,7 @@ CMakeFiles/wino-mail-qt.dir/src/ui/maillistview.cpp.o: /mnt/c/Users/javie/Docume
   /usr/include/x86_64-linux-gnu/qt6/QtWidgets/qlistview.h \
   /usr/include/x86_64-linux-gnu/qt6/QtWidgets/qpushbutton.h \
   /usr/include/x86_64-linux-gnu/qt6/QtWidgets/qrubberband.h \
+  /usr/include/x86_64-linux-gnu/qt6/QtWidgets/qscrollbar.h \
   /usr/include/x86_64-linux-gnu/qt6/QtWidgets/qsizepolicy.h \
   /usr/include/x86_64-linux-gnu/qt6/QtWidgets/qslider.h \
   /usr/include/x86_64-linux-gnu/qt6/QtWidgets/qstackedwidget.h \
@@ -42707,10 +42709,6 @@ wino-mail-qt_autogen/GQ6NBGVJMG/moc_accountservice.cpp:
 
 /usr/include/x86_64-linux-gnu/qt6/QtGui/QTextImageFormat:
 
-/usr/include/x86_64-linux-gnu/qt6/QtWidgets/qscrollbar.h:
-
-/usr/include/x86_64-linux-gnu/qt6/QtWidgets/QScrollBar:
-
 /usr/include/x86_64-linux-gnu/qt6/QtWidgets/QGraphicsDropShadowEffect:
 
 /usr/include/x86_64-linux-gnu/qt6/QtGui/QTextDocument:
@@ -42729,6 +42727,10 @@ wino-mail-qt_autogen/GQ6NBGVJMG/moc_accountservice.cpp:
 
 /usr/include/x86_64-linux-gnu/qt6/QtGui/QCloseEvent:
 
+/usr/include/x86_64-linux-gnu/qt6/QtWidgets/qscrollbar.h:
+
+/usr/include/x86_64-linux-gnu/qt6/QtWidgets/QScrollBar:
+
 /usr/include/x86_64-linux-gnu/qt6/QtGui/QCursor:
 
 /usr/include/x86_64-linux-gnu/qt6/QtWidgets/qfiledialog.h:

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

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- /usr/include/x86_64-linux-gnu/qt6/QtCore/QRect
+ /usr/include/x86_64-linux-gnu/qt6/QtCore/QRect \
+ /usr/include/x86_64-linux-gnu/qt6/QtWidgets/QScrollBar \
+ /usr/include/x86_64-linux-gnu/qt6/QtWidgets/qscrollbar.h