Add two orphaned actions to the menus, drop two dead members

Both actions already exist and work; they were simply only reachable from
a toolbar, and those toolbars are user-hideable via Configuration >
Afficher, so hiding one made the feature unreachable entirely.

- "Afficher les guides" (m_draw_guides) goes into the Affichage menu next
  to "Afficher la grille". The two are adjacent lines in the view toolbar
  and do the same kind of thing, but only the grid had a menu entry.

- "Creation automatique de conducteur(s)" (m_auto_conductor) goes into the
  Projet menu. It writes a project setting via
  QETProject::setAutoConductor(), so the Projet menu is where a user would
  look for it; it is placed with the project properties, above a separator
  that keeps the folio operations grouped as before.

Also removes conductor_default and m_project_folio_list from the header.
Both are declared but never allocated and never referenced anywhere in the
tree -- that the build still links is the proof they were dead.

No new strings: both actions already carry translated text.

Found while auditing every QAction against every menu, discussion #677.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

sources/qetdiagrameditor.cpp

@@ -882,6 +882,8 @@ void QETDiagramEditor::setUpMenu()
 
 	// menu Projet
 	menu_project -> addAction(m_project_edit_properties);
+	menu_project -> addAction(m_auto_conductor);
+	menu_project -> addSeparator();
 	menu_project -> addAction(m_project_add_diagram);
 	menu_project -> addAction(m_remove_diagram_from_project);
 	menu_project -> addAction(m_clean_project);
@@ -917,6 +919,7 @@ void QETDiagramEditor::setUpMenu()
 	menu_affichage -> addAction(m_mode_visualise);
 	menu_affichage -> addSeparator();
 	menu_affichage -> addAction(m_draw_grid);
+	menu_affichage -> addAction(m_draw_guides);
 	menu_affichage -> addAction(m_grey_background);
 	menu_affichage -> addSeparator();
 	menu_affichage -> addActions(m_zoom_actions_group.actions());