ci: force Python 3.12 for build.yml

- force Python 3.12 for build.yml to ensure PySide6 compatibility

Author: leafspark

.github/workflows/build.yml

@@ -29,7 +29,7 @@ jobs:
     - name: Set up Python
       uses: actions/setup-python@v5
       with:
-        python-version: '3.x'
+        python-version: '3.12'
         architecture: ${{ matrix.arch }}
 
     - name: Install dependencies