[Feature Request]: Data Backup and Restore functionality

### Preflight Checklist

- [x] I have read the [Contributing Guidelines](https://github.com/EnAccess/micropowermanager/blob/main/CONTRIBUTING.md) for this project, if it exists.
- [x] I agree to follow the [Code of Conduct](https://github.com/EnAccess/micropowermanager/blob/main/CODE_OF_CONDUCT.md) that this project adheres to.
- [x] I have searched the [issue tracker](https://github.com/EnAccess/micropowermanager/issues) for a feature request that matches the one I want to file, without success.

### Problem Description

MicroPowerManager is an OpenSource project and multiple instances of MPM might exist. I.e. a self-hosted version on client's premises or the EnAccess-hosted version.

To prevent lock-in effect and ensure future proof operations it should be possible to seamlessly migrate client data between two different instances of MPM.

For example a user of the EnAccess-hosted version might want to move to their own self-hosted version (or vice-versa).

### Proposed Solution

Implement the following two features

- Data Backup to File
- Restore from Backup from File

These features should be implemented per "Tenant".

### Alternatives Considered

N/A

### Additional Information

_No response_