Implement and backfill canonical scientific QA diagnostics

[jakobtfaber]

Question

Implement the approved structured QA contract and dashboard-composed scientific inspection view, including the source-centric and signed renderers, coverage/weights, overlays, cutouts, three-gate evidence, provenance, explicit missing/failure states, and backfill for every stored hourly-epoch mosaic without rerunning imaging. What implementation and validation evidence demonstrates that the approved contract and full backfill acceptance are met?