v0.5.54 release (latest)

v0.5.54 release notes for the GitHub Release v0.5.54 (release task: Issue #1456).

Tag state (verified against origin)

Ref	Object	Points at
`v0.5.54`	annotated tag `9398631ff6e5c238f6c4b88cec91424d020f6155`	commit `5ab4a7e2b2e18bedcd6bdbe0162b6bf0a85e4ac6`

Revert #1450: a rejected model API key must not mark the ticket ai-blocked (Issue #1455; PR #1457)