fix: update codecov-action to v4 for compatibility

- Replace codecov/codecov-action@v6 with @v4 (latest stable)
- Fix CI failures due to unavailable v6 version
- Ensure consistent codecov integration across all workflows

Author: thc1006

.github/workflows/ci.yml

@@ -327,7 +327,7 @@ jobs:
         path: ${{ env.COMPONENT_PATH }}/coverage.*
 
     - name: Upload coverage to Codecov
-      uses: codecov/codecov-action@v6
+      uses: codecov/codecov-action@v4
       if: env.COMPONENT_PATH != ''
       with:
         file: ${{ env.COMPONENT_PATH }}/coverage.out