Epic: E10 — Observation history capture

[kylejb]

Hourly GitHub Actions cron archives raw mapped-buoy observations to Postgres — the irreplaceable data clock (NDBC realtime is a rolling ~45-day window). Starts ASAP, parallel to M0.

Milestone: M0 / early.

Sub-issues

• M0-3 — Observation ingestion cron (GitHub Actions) #210 — M0-3 Observation ingestion cron (GitHub Actions)