Module @vektorprogrammet/database/placements

Database-backed Placements, roster notification delivery, and reviewed cohort import. Import from @vektorprogrammet/database/placements in a trusted server runtime. Private adapter modules are not supported import paths. Cohort imports take one native SqlClient. Reports describe current facts and provenance; they become durable only when the outermost transaction commits. Nested callers own that atomic cutover boundary and publish their receipt only after commit.