Mouse gestures: own command list, 4 or 8 directions

The right-drag ring showed the shortcut bar's commands for the selection.
A new Preferences page, "Gestes de la souris", lets the user pick the
ring's commands per selection context, one per direction, and choose 4 or
8 directions. Commands are dropped from the list onto a slot of a ring
editor, or placed with a button; Delete empties a slot.

A context the user never edits keeps following the shortcut bar, and 8
directions stays the default, so nothing changes for anyone who does not
open the page. A picked list is positional: a direction left empty, or
holding a command this build lacks, stays empty instead of shifting the
others. Stored like ShortcutBarSettings: diagrameditor/gestures/<context>
id lists in QSettings, defaults not stored.

tst_gesturesettings covers the defaults, positional lists, the 4/8
setting, the overlay's sectors and empty slots, and the page.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

cmake/qet_compilation_vars.cmake

@@ -307,6 +307,8 @@ set(QET_SRC_FILES
   ${QET_DIR}/sources/diagramcontexttoolbar.h
   ${QET_DIR}/sources/diagramgestureoverlay.cpp
   ${QET_DIR}/sources/diagramgestureoverlay.h
+  ${QET_DIR}/sources/gesturesettings.cpp
+  ${QET_DIR}/sources/gesturesettings.h
   ${QET_DIR}/sources/commandsearchpopup.cpp
   ${QET_DIR}/sources/commandsearchpopup.h
   ${QET_DIR}/sources/titleblockcell.cpp
@@ -860,6 +862,8 @@ set(QET_SRC_FILES
   ${QET_DIR}/sources/ui/configpage/shortcutbarconfigpage.h
   ${QET_DIR}/sources/ui/configpage/toolbarsconfigpage.cpp
   ${QET_DIR}/sources/ui/configpage/toolbarsconfigpage.h
+  ${QET_DIR}/sources/ui/configpage/gesturesconfigpage.cpp
+  ${QET_DIR}/sources/ui/configpage/gesturesconfigpage.h
 
   ${QET_DIR}/sources/undocommand/addelementtextcommand.cpp
   ${QET_DIR}/sources/undocommand/addelementtextcommand.h