PUT /api/activity/custom-language-list/

Replace or upsert the caller's organization Custom Language List from a bulk upload. Each {term, category, severity} row's term is canonicalized (lowercase + trimmed) and duplicate terms in one batch are collapsed last-wins. Re-uploading a term updates its category/severity in place; when replace is true, terms absent from the upload are also deleted so the stored list matches the file exactly. upserted / deleted count terms. Admin/manager + activity-tracking flag gated; scoped to the caller's organization.