Replace stub metrics provider with real QuestDBMetricsProvider that
queries QuestDB via PostgreSQL wire protocol (port 8812) for rolling
model Sharpe, win rates, confidence buckets, and ensemble metrics.
- Add QuestDB service to docker-compose.yml (8.2.3, ports 9009/8812/9003)
- Create questdb_metrics.rs with 5 SQL queries and graceful fallback
- Wire QuestDBMetricsProvider into main.rs (replaces StubMetricsProvider)
- Fix unused Instant import in feedback_loop.rs (#[cfg(test)] scope)
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
FeedbackLoop runs as a background tokio task, periodically running
weight and gate optimization cycles with kill switch monitoring and
retraining trigger detection. Wired into main.rs with a stub
MetricsProvider until QuestDB is deployed.
7 new tests covering kill switch, freeze/unfreeze, retraining triggers.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
