Phase 10 deferred items

Out-of-scope issues found while executing Phase 10 plans. They are not caused by Phase 10 changes and are not fixed here.

From 10-01

fonoteka.go parity package fails two tests before Phase 10. TestMigrateSeedsCanonicalGenres expects no summer_migrations_summercms_cabana history table, and TestSchemaMatchesPHPSnapshot reports backend_users, backend_user_roles and backend_jwt_blacklist as unexpected extra tables. All four come from the Phase 9 cabana migrations. Reproduced on untouched copies of both repositories at the pre-10-01 commits (summercms.go 8c3e131, fonoteka.go feaca6b), so go test ./... in fonoteka.go was already red in this package. Fix belongs to a Phase 9 follow-up: add the cabana history table and the three backend tables to the parity allow-lists with a reason.
gofmt -l lists internal/build/registry.go in summercms.go. Pre-existing, untouched by Phase 10.