[BUG] Fix STAC license

[jjcfrancisco]

STAC CI validation failing due to invalid license fields per STAC spec.

Root causes

TYPE_LICENSE_MAP:

type	problem	fix
land_cover	leading tab in value	"CC-BY-4.0"
building_part	missing → emits null	"ODbL-1.0"
address	spaces fail SPDX regex	"other" + license link
place	commas fail SPDX regex	"other" + license link

Also: add rel=license attribution link to all collections. Remove allowed-to-fail: "stac-validate" in ci.yaml:142 once fixed.

Closes #58