Simplify bandit nosec comments and mock metrics_controller with real spe
- drift.py/simple_metrics.py: move nosec rationale to a code comment above
the query instead of an inline suppression comment, keeping bandit happy
with a plain `# nosec`
- tests: replace bare `MagicMock()` with `MagicMock(spec=MetricsController)`
for metrics_controller across activities/repository tests so mocks fail
fast on attribute typos instead of silently accepting any call