chore(migrations): upgrade atlas to v1.3.8 and track it with dependabot
Merged
MI
21h ago+35+35+01234567890123456789-23-23-01234567890123456789
Upgrades Atlas from v1.3.4 to v1.3.8: the migrations container image, the CLI version installed by make init, and the version used in the test workflow.
Adds a docker ecosystem entry to the Dependabot configuration so Atlas image upgrades are proposed automatically (weekly, with a 7-day cooldown). The golang image stays ignored because Go upgrades are coordinated with go.mod through the upgrading-golang skill. The Atlas image is now pinned by tag and digest so Dependabot can resolve its version. Dependabot only updates the image, so ATLAS_VERSION in common.mk and .github/workflows/test.yml still has to be bumped in the same PR.
AI disclosure: this change was made with assistance from Claude Code.