- Silo_ToggleMode: checkable toolbar button that swaps Ctrl+O/S/N
between standard FreeCAD file commands and Silo equivalents
- _swap_shortcuts() helper stores/restores original QAction shortcuts
- SSL settings: add CA certificate file browser (SslCertPath preference)
with QFileDialog for .pem/.crt/.cer, loaded in _get_ssl_context()
- Integrate Silo_BOM into workbench toolbar (after upstream BOM merge)
- Add Silo_ToggleMode to toolbar as first item with separator