- D5: bump lib-auth-guard v0.2.0 -> v0.2.1 (internal httpx error
  handling fix, no public API change), regenerate poetry.lock
- D3: remove orphan src/settings/mico_service_settings.py (unused,
  not wired into config.py) + its coverage omit entry
- D4: drop stale coverage omit entries for non-existent files
  (mongo_db_settings.py, postgres_settings.py, s3_settings.py)

pytest 138 passed, coverage 98.92%, ruff G/LOG clean.