🧹 chore: fix all lint issues in domain_test.go

- errcheck: handle errors from io.ReadAll(resp.Body) with require.NoError
- httpNoBody: use http.NoBody instead of nil in httptest.NewRequest
- fieldalignment: reorder struct fields to minimize padding
- errcheck: add error handling in benchmarks for app.Test

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>