Use Python 3.12.12 in CI workflow

Update .github/workflows/build-python.yml to change PYTHON_VERSION from 3.13.12 to 3.12.12. PYTHON_DIST_RELEASE remains unchanged. This ensures the CI uses the 3.12.12 Python build.

Author: FeodorFitsner

.github/workflows/build-python.yml

@@ -7,7 +7,7 @@ on:
   workflow_dispatch:
 
 env:
-  PYTHON_VERSION: 3.13.12
+  PYTHON_VERSION: 3.12.12
   PYTHON_DIST_RELEASE: 20260203 # https://github.com/astral-sh/python-build-standalone/releases
 
 jobs: