chore(ci): upgrade GitHub Actions to v4/v5 and add Dependabot config

- Upgrade actions/checkout from v1 to v4
- Upgrade actions/setup-python from v1 to v5
- Add Dependabot config for pip and GitHub Actions weekly updates

.github/workflows/pythonapp.yml

@@ -8,9 +8,9 @@ jobs:
     runs-on: windows-latest
 
     steps:
-    - uses: actions/checkout@v1
+    - uses: actions/checkout@v4
     - name: Set up Python 3.13
-      uses: actions/setup-python@v1
+      uses: actions/setup-python@v5
       with:
         python-version: '3.13'
     - name: Install dependencies