Existing Docker volumes crashed at startup because ensureAuthTables indexed
token_hash before the column existed on upgraded auth.db files. Bump images to 3.0.0.
Wire docker-publish to git tags v*, workflow_dispatch tag input, and
semver prereleases; pin quick-start compose to 3.0.0-alpha by default.
Co-authored-by: Cursor <cursoragent@cursor.com>