Sketcher: Implement a Euler spiral curve (for civil engineering)

### Is there an existing issue for this?

- [x] I have searched the existing issues

### Problem description

Request to implement the Euler spiral curve in Sketcher so that we can design the civil engineering route in the sketch.
If there is no implementation plan, I am willing to implement this feature, but I have no experience, can you guide me on how to implement it or some idea
Thanks!

### Full version info

```shell
OS: Windows 11 build 26100
Architecture: x86_64
Version: 1.1.0dev.42605 (Git)
Build date: 2025/07/18 16:20:04
Build type: Release
Branch: main
Hash: da5e18f5d8e7eb4df89c86c9562599435b5c5187
Python 3.11.13, Qt 6.8.3, Coin 4.0.3, Vtk 9.3.1, boost 1_86, Eigen3 3.4.0, PySide 6.8.3
shiboken 6.8.3, xerces-c 3.2.5, IfcOpenShell 0.8.2, OCC 7.8.1
Locale: Chinese/China (zh_CN)
Navigation Style/Orbit Style/Rotation Mode: Revit/Trackball/Object center
Stylesheet/Theme/QtStyle: unset/FreeCAD Classic/fusion
Logical DPI/Physical DPI/Pixel Ratio: 96/93.0817/1
Installed mods:
* framework
* geodata
* Geomatics
* Reinforcement
* Road 2025.2.6
* woodworking 0.21.2.33771.0.24.1
```

### Subproject(s) affected?

None

### Anything else?

_No response_

### Code of Conduct

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