feat(ui): replace app-menu logo with a quick-access file toolbar

Remove the OCS-logo button and the dropdown menu it opened; the top strip
now shows direct New / Open / Save / Save As / Print buttons ahead of the
undo/redo controls. Drop the HELP and OPTIONS commands (HELP dumped text to
the command line, OPTIONS aliased the drafting-settings popup).

The app-menu overlay is gone, so its rendering code, MENU_ITEMS, four dead
messages, and the LOGO_RED / GEAR / HELP assets are removed. The recents
list it held is the only survivor — moved into OpenCADStudio.recent_files
via a new app/recent.rs, backing the Start page's Recent Documents panel.

Quick-access icons are redrawn in a cleaner style (file-plus, folder-open,
device-floppy, file-export, printer) and tinted light so they read on the
dark strip; FOLDER / DOC keep their old glyphs for the file browser.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

assets/icons/ui/folder_open.svg

@@ -0,0 +1 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 24 24" fill="none" stroke="#000000" stroke-width="2" stroke-linecap="round" stroke-linejoin="round"><path d="M5 19l2.757 -7.351a1 1 0 0 1 .936 -.649h12.307a1 1 0 0 1 .986 1.164l-.996 5.211a2 2 0 0 1 -1.964 1.625h-14.03a2 2 0 0 1 -2 -2v-11a2 2 0 0 1 2 -2h4l3 3h7a2 2 0 0 1 2 2v2"/></svg>