Custom Dance School Management Software Development

Title: Senior developer required for custom dance school management software
I am looking for an experienced senior developer or small development team to build a custom management system for a dance school in Switzerland.
The solution must work on both desktop and mobile, preferably through a responsive web application unless you recommend a more suitable architecture.
Required features
- Online student registration for classes
- Flexible billing based on student age and number of classes attended per week
- Invoice generation with Swiss QR payment code
- Point-card management for drop-in classes
- Attendance tracking for students and teachers
- Automatic matching of bank payments with invoices
- Automatic reminders for unpaid invoices
- Import/migration of existing student data and historical records
- Initial user training and technical support
Please include the following in your proposal
1. Recommended architecture: web app, PWA, mobile app or other
2. Proposed technology stack
3. Estimated development time
4. Estimated total fixed-price budget
5. Your hourly or daily rate
6. Proposed project phases and milestones
7. How you would implement Swiss QR invoices
8. How you would implement bank payment reconciliation
9. What banking format/API you would use, e.g. CAMT or another method
10. How you would handle migration of existing Excel/CSV data
11. Hosting recommendation and estimated recurring hosting costs
12. Maintenance/support costs after launch
13. Testing and warranty period included
14. Whether full source code and ownership are transferred to the client
15. Any third-party licences or recurring costs required
16. Examples of similar business-management applications you have developed
17. What information you still need before providing a final fixed-price quotation
I am looking for a realistic commercial proposal, including architecture, total cost, delivery time, recurring costs and technical approach.
Remote work is fully acceptable.