feat(ui): classic pull-down menu bar and ribbon toggle

MENUBAR 1 shows File, Edit, View, Insert, Format, Tools, Draw,
Dimension, Modify, Parametric and Help menus above the ribbon; every
entry runs an existing command, and a test keeps each entry pointing at
a registered command. RIBBONCLOSE hides the ribbon and RIBBON brings it
back, so the menus can replace it. Both choices persist.

Also translates the "File" label, which every locale had left in
English.

Refs #1450

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

src/app/mod.rs

@@ -642,6 +642,10 @@ pub(super) struct OpenCADStudio {
     pick_box: i32,
     /// HPASSOC: new hatches follow their boundary objects.
     hatch_associative: bool,
+    /// MENUBAR: the classic pull-down menus show above the ribbon.
+    show_menu_bar: bool,
+    /// RIBBONCLOSE hid the ribbon; RIBBON brings it back.
+    ribbon_closed: bool,
     /// Use REFEDIT rather than BEDIT when double-clicking an attribute-free block.
     double_click_block_refedit: bool,
     /// Open ATTEDIT when double-clicking a block with attributes.
@@ -4543,6 +4547,8 @@ impl OpenCADStudio {
             cursor_size: 5,
             pick_box: 3,
             hatch_associative: true,
+            show_menu_bar: false,
+            ribbon_closed: false,
             double_click_block_refedit: false,
             double_click_block_attedit: true,
             right_click_mode: settings::RightClickMode::ShortcutMenu,