fix(ci): correct YAML syntax and update deprecated GitHub Actions

YAML Syntax Fix:
- Fix malformed indentation on line 60 (missing proper step structure)
- Ensure all steps are properly aligned and formatted

GitHub Actions Updates:
- actions/setup-python@v4 → v5 (latest stable)
- pdm-project/setup-pdm@v3 → v4 (latest stable)
- actions/cache@v3 → v4 (latest stable)
- actions/upload-artifact@v3 → v4 (fixes deprecation error)

The workflow should now run without syntax errors or deprecation warnings.

.github/workflows/ci.yml

@@ -34,17 +34,17 @@ jobs:
         uses: actions/checkout@v4
 
       - name: Set up Python 3.10
-        uses: actions/setup-python@v4
+        uses: actions/setup-python@v5
         with:
           python-version: '3.10'
 
       - name: Install PDM
-        uses: pdm-project/setup-pdm@v3
+        uses: pdm-project/setup-pdm@v4
         with:
           python-version: '3.10'
 
       - name: Cache PDM dependencies
-        uses: actions/cache@v3
+        uses: actions/cache@v4
         with:
           path: |
             ~/.cache/pdm
@@ -62,7 +62,7 @@ jobs:
           pdm ci
 
       - name: Upload test results
-        uses: actions/upload-artifact@v3
+        uses: actions/upload-artifact@v4
         if: always()
         with:
           name: test-results-${{ github.run_number }}