Add restocking view, reports i18n, and new API endpoints

[faizu6]

Summary

• Add new Restocking page with budget-based priority recommendations derived from demand forecasts, including order submission and tracking
• Refactor Reports view from Options API to Composition API with full i18n (English/Japanese) and filter support
• Add backend API endpoints for quarterly reports, monthly trends, restocking recommendations, and submitted orders
• Add submitted restocking orders section to the Orders view
• Expand inventory data with 8 new items (widgets, bearings, gaskets, motors, filters, valves, sensors, controllers)
• Add backend test coverage for reports endpoints

Test plan

• Verify Restocking page loads recommendations and respects budget input
• Verify restocking order submission creates an order and appears in Orders view
• Verify Reports page displays quarterly and monthly data with filters applied
• Verify language switching works for all new restocking and reports translations
• Run pytest tests/backend/test_reports.py to confirm backend tests pass
• Verify new inventory items appear on the Inventory page

🤖 Generated with Claude Code