- Add AdminProfilePage component for admin to edit own data
- Add 'Stammdaten' menu item in admin navigation
- Add route /admin/stammdaten for the new page
- Use existing POST /api/portal/users endpoint to save changes
- Update session context after successful save
- Add SystemPricing domain model to store monthly price in MongoDB
- Add SystemPricingRepository for database access
- Add SystemPricingService with get/save functionality
- Add SystemPricingController with GET/POST endpoints (admin only)
- Add PricingPage component for frontend
- Add navigation menu item for Preistabelle (above Rechnung)
- Add route /admin/preistabelle for the new page
- Add 'Rechnung' menu with sub-items 'Verwalten' and 'Template' in admin sidebar
- Create InvoiceTemplatePage with drag-and-drop editor for invoice templates
- Includes invoice-specific elements (header, customer data, issuer info,
invoice items, totals, payment terms, bank details)
- Supports PDF preview and download
- API integration for saving/loading templates (/admin/invoice-template)
- Create InvoiceManagementPage as placeholder for invoice overview
- Add routes for /admin/rechnung/verwalten and /admin/rechnung/template
- Update page titles in AppShell for new routes
