What's new
• Multi-language UI (English / Deutsch): Switch the interface language from any screen using the language selector. Labels across the toolbar, file summary, validation
panel, booking table, startup, error, and drag-and-drop views update immediately.
• Locale-aware totals: Monetary totals use locale-appropriate number formatting (e.g. 1,234.56 in English, 1.234,56 in German).
• Language preference is remembered between app restarts.
Fixes & improvements
• Added a Close File button to the toolbar for quicker workflow.
• Improved macOS dev/build reliability via the Tauri wrapper script.
• Updated About dialog with author and copyright information.
Note: Native macOS menus, window title, and backend validation/error messages remain in English by design.