SCIM DELETE /Users/{id} previously called litellm_usertable.delete without
clearing rows that FK back to the user, so Postgres rejected the delete with
LiteLLM_InvitationLink_user_id_fkey and the SCIM caller saw a 500. Add a
helper to drop invitation_link, organization_membership, and team_membership
rows before the user delete (mirrors /user/delete in internal_user_endpoints).
Also add a Status column to the Virtual Keys and Internal Users tables so
admins can see at a glance which keys are blocked and which users SCIM has
deactivated. SCIM-blocked keys carry a tooltip explaining the origin.
Pin the dashboard's Node version to 20 via .nvmrc to match CI.
