FEM: mesh export units

### Is there an existing issue for this?

- [x] I have searched the existing issues

### Problem description

I have created a 3D geometry using [m] as the unit of measurement. I have generated a FE mesh, using both Gmsh and Netgen. When exporting the mesh, the node coordinates appear to be in [mm]. Changing the project system of units does not appear to affect the exported file coordinates.

Ideally, the exported coordinate units should match the ones used in the project in order to avoid having to convert them later.

Thanks!

[example.zip](https://github.com/user-attachments/files/20080812/example.zip)

### Full version info

```shell
OS: Windows 10 build 19045
Architecture: x86_64
Version: 1.0.0.39109 (Git) Conda
Build type: Release
Branch: (HEAD detached at 1.0.0)
Hash: 2fcc5317fe3aee96ca73475986a577719fc78e20
Python 3.11.10, Qt 5.15.15, Coin 4.0.3, Vtk 9.3.0, OCC 7.8.1
Locale: English/United States (en_US)
Stylesheet/Theme/QtStyle: FreeCAD Dark.qss/FreeCAD Dark/Fusion
```

### Subproject(s) affected?

None

### Anything else?

_No response_

### Code of Conduct

- [x] I agree to follow this project's Code of Conduct