🔧 fix(ci): update upload-artifact to v4

- Update deprecated actions/upload-artifact@v3 to v4
- Fixes GitHub Actions failure on artifact upload

🤖 Generated with Claude Code

Co-Authored-By: Claude <noreply@anthropic.com>

Author: christopher-igweze

.github/workflows/tests.yml

@@ -46,7 +46,7 @@ jobs:
 
     - name: Archive coverage report
       if: always()
-      uses: actions/upload-artifact@v3
+      uses: actions/upload-artifact@v4
       with:
         name: coverage-report-py${{ matrix.python-version }}
         path: htmlcov/