ci: merge coverage into CI and use codecov v5

Author: Yuyz0112

.github/workflows/ci.yml

@@ -31,7 +31,11 @@ jobs:
 
       - run: bun install
 
-      - run: bun test
+      - run: bun test --coverage --coverage-reporter=lcov
+      - name: Upload coverage reports to Codecov
+        uses: codecov/codecov-action@v5
+        with:
+          token: ${{ secrets.CODECOV_TOKEN }}
 
   build:
     runs-on: ubuntu-latest