D3: LSE cross-check — latest oracle close vs LSE close, emit divergence signal

Hourly cross-check: fetches LSE daily close for each covered metal, compares against the most recent settled Pyth bar, emits divergence signal and stale/high-divergence alerts. FOUNDER-GATED: needs LSE_API_KEY.

pg_cron schedule: every 60 minutes. Dead-man 2x = lse_confirmation_interval_minutes * 2.