- Add .golangci.yml with sensible linting rules
- Add Makefile with test, lint, fmt, vet, build targets
- Enhance CI pipeline with Go formatting check and golangci-lint job
- Create shared testutil.FakeRepository for handler tests
- Refactor handler tests to use shared FakeRepository
- Add data/ and coverage.out to .gitignore
Co-Authored-By: Paperclip <noreply@paperclip.ing>