Add support for Python 3.13 on Windows

[freakboy3742]

Describe the bug

Toga can't currently be installed on Windows using Python 3.13.

This is due to pythonnet/pythonnet#2454.

Steps to reproduce

1. Install Python 3.13
2. pip install toga~=0.4.0

The installation will fail with an error that it Could not find a version that satisfies the requirements pythonnet>=3.0.0 (from toga-winforms) (from versions: 2.0.0, ...

Expected behavior

Toga should be installable on Windows.

Screenshots

No response

Environment

• Operating System: Windows
• Python version: 3.13
• Software versions:
  • Briefcase: 0.3.19+
  • Toga: 0.4.6+

Logs

No response

Additional context

There's nothing required on the Toga side of this problem - it's entirely an upstream issue.

[Jzhenli]

will support disable GIL? @freakboy3742

[mhsmith]

No, we'll follow the default setting on all platforms, which means the GIL will still be present in 3.13.