Switch to official .NET with next Debian

### Describe the feature

[Mono](https://www.mono-project.com/) is not active anymore and recommends all users to switch to official [dotnet runtime](https://github.com/dotnet/runtime/tree/main/src/mono). We should do this for the next Debian release. Avoid doing this earlier to not break users.

### Use Case

n/a

### Proposed Solution

_No response_

### Other Information

_No response_

### Acknowledgements

- [ ] I may be able to implement this feature request
- [ ] This feature might incur a breaking change

Start by locating the Debian-based image build configuration and the places where Mono is installed or referenced. Confirm how the next Debian release is selected, then replace Mono with the official dotnet runtime only for that release; done means the image builds successfully without breaking earlier supported releases.

Written by the indexing model from the issue text.