Add SQLite-backed sovereignty metrics store that tracks research
sovereignty progress (cache hit rate, API cost, time-to-report,
human involvement, local artifacts) against graduation targets.
- infrastructure/sovereignty_metrics.py: metrics store with alert
thresholds, trend data, and event bus integration
- dashboard/routes/sovereignty_metrics.py: JSON API + HTMX partial
- Sovereignty metrics panel on Mission Control dashboard
- Config setting for API cost alert threshold
- 17 tests covering store, alerts, emit, and route endpoints
Fixes#981
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>