[turban]

With dhis2/open-climate-service#470, a dataset can leave out period_type: it has no time axis, its plugin implements fetch(bbox), and the store is (y, x). copdem90_elevation_static now works like core's copdem30_elevation_static:

• Template: no period_type or temporal extent, sync: kind: static. It was a one-year series with 2021, the release year, as a fake period.
• Plugin: fetch(bbox) replaces periods() and fetch_period(), and no time axis is added. Tile selection and the mosaic are unchanged.
• Tests call fetch and check the result is (y, x).
• The lock moves OCS to a main that includes #470.

An existing store has a t axis, so it needs ingesting again with overwrite.

Verified on the Nepal test instance: re-ingested in 27 s as a (y, x) store (4921 x 9781, highest cell 8,726 m), with no period type or time range on the dataset, and a thumbnail. Tests pass and lint is clean.