Bump codecov-action from v6.0.0 to v7.0.0 (#4298)

v7.0.0 fixes GPG signature verification failures caused by Codecov
rotating their signing key in CLI v11.x.

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: imnasnainaec

.github/workflows/backend.yml

@@ -93,7 +93,7 @@ jobs:
         with:
           name: coverage
       - name: Upload coverage report
-        uses: codecov/codecov-action@57e3a136b779b570ffcdbf80b3bdc90e7fab3de2 # v6.0.0
+        uses: codecov/codecov-action@fb8b3582c8e4def4969c97caa2f19720cb33a72f # v7.0.0
         with:
           token: ${{ secrets.CODECOV_TOKEN }}
           fail_ci_if_error: true

.github/workflows/frontend.yml

@@ -117,7 +117,7 @@ jobs:
         with:
           name: coverage
       - name: Upload coverage report
-        uses: codecov/codecov-action@57e3a136b779b570ffcdbf80b3bdc90e7fab3de2 # v6.0.0
+        uses: codecov/codecov-action@fb8b3582c8e4def4969c97caa2f19720cb33a72f # v7.0.0
         with:
           token: ${{ secrets.CODECOV_TOKEN }}
           fail_ci_if_error: true