Reorganise tests/ into category folders (unit, system, SIT, performance, uat) #167

Context

Backend test organisation follow-up from closed PR #41.

PR #41 (23 days old, Draft) proposed reorganising tests/ into six category folders: unit/, system/, system_integration/, performance/, accessibility/, uat/. It also added shared fixtures in tests/conftest.py (live_api, registry_cleanup, te_org_cleanup, destructive_enabled) and new Makefile targets (test-unit, test-system, test-sit, test-performance, test-accessibility, test-uat).

The reorganisation is still valuable — the current flat tests/*.py layout makes it hard to run just one category, and the new M2/M3 tests have landed in the flat folder with no categorisation.

Scope

• Move existing tests/*.py into category folders (same renames Group tests into unit, system, SIT, performance, accessibility and UAT #41 proposed)
• Create tests/conftest.py with the four shared fixtures
• Add Makefile targets for each category
• Update pytest.ini with the new markers (system, sit, performance, accessibility, uat)
• Update scripts/lint.sh PY_TESTS list to the new paths plus the 9 M2/M3/preflight tests that landed after Group tests into unit, system, SIT, performance, accessibility and UAT #41 was drafted (test_api_hardening.py, test_evals_tier_e_x.py, test_migrations.py, test_import_counts.py, test_accounts.py, test_tenant_isolation.py, test_roles.py, test_oidc.py, test_preflight_ps1.py)
• Update requirements-dev.txt with playwright and axe-playwright-python (needed by #B below)

Out of scope

• Frontend test reorganisation under csv-table-hub-main/src/__tests__/unit/ (that code is from Lovable, see Live pointers to superseded docs/API_INTEGRATION.md need to be resolved #164 and STARTER_GUIDE.md walkthrough skips sign-in step (Milestone 2 landed after PR #63 was drafted) #166 for context; a Streamlit spike Spike: rebuild M4 review screen in Streamlit (1-day time-box) #154 is active)
• The new test files Group tests into unit, system, SIT, performance, accessibility and UAT #41 added (test_system_api.py, test_sit_frontend_contract.py, test_performance.py, test_uat_user_stories.py, test_config_auth.py, test_csv_parse.py, test_db_pool.py) — those become smaller follow-ups once the structure is in place

Done when

• tests/ has the six category folders, each with an __init__.py and the moved files
• make test-unit, make test-system etc work locally
• python -m pytest tests/ -q still passes with the same test count
• scripts/lint.sh lists every Python test file in the repo

Related

• Group tests into unit, system, SIT, performance, accessibility and UAT #41 (closed, superseded by this + #B + #C)
• #B: Accessibility CI job
• #C: Test catalogue generator
• Live pointers to superseded docs/API_INTEGRATION.md need to be resolved #164, STARTER_GUIDE.md walkthrough skips sign-in step (Milestone 2 landed after PR #63 was drafted) #166: STARTER_GUIDE pointer fixes (independent)
• Spike: rebuild M4 review screen in Streamlit (1-day time-box) #154: Streamlit spike (may change the frontend-test picture)