[enhancement]: convert model to 16-bit

### Is there an existing issue for this?

- [X] I have searched the existing issues

### Contact Details

_No response_

### What should this feature add?

Sometimes models are only distributed in 32-bit format, but we're only interested in running them at 16-bit.

To save disk space and loading time, model manager should have a "convert to 16-bit" button that writes out float16 safetensors and deletes the old files.

### Alternatives

_No response_

### Aditional Content

In order to know whether models need converting to 16-bit or not, we first need to be able to see their data type:
- #4068