add lucide-react dependency and update form handling in MainForm

- Added lucide-react to package dependencies
- Refactored MainForm to improve form handling and user selection
- Removed SuccessPage component and related logic
- Updated localization files to include new keys for invoice details
- Created interfaces for form data and messages

frontend/src/utils/i18n/locales/de/de.json

@@ -4,6 +4,7 @@
     "phone-number": "Telefonnummer",
     "tickets": "Lose",
     "invoice": "Rechnung",
+    "invoice-details": "Rechnungsdetails",
     "company-name": "Firmenname",
     "street": "Straße + Haus Nr.",
     "postal-code": "Plz + Stadt",