Consolidation pass: HR-only access, effective-dated mutations, data integrity guards, test suite

Reworks the app from a two-role (hr_admin/manager) model to a single
HR-only role gated by profiles.is_active, fixes transfer/promote/karenz/
reorg RPCs to actually defer future-dated changes via a new
pending_org_changes table instead of writing them immediately (applied
by a daily Vercel Cron route), makes reorg undo append-only instead of
deleting history, adds Karenz-return and history-date integrity guards,
deprecates the salary column, and adds explicit schema grants + perf
indexes needed to run against a fresh (non-hosted) Postgres instance.

Adds vitest unit + integration test suites (the latter against a real
local Supabase instance) covering all of the above, plus lint/typecheck/
build wiring (`npm run check`).

app/(app)/orgchart/page.tsx

@@ -14,7 +14,7 @@ export default async function OrgChartPage() {
     { data: reorgScenarios },
   ] = await Promise.all([
     supabase
-      .from("employees_directory")
+      .from("employees")
       .select("id, personnel_number, first_name, last_name, job_title, manager_id, team_id, division_id, is_lead, org_level")
       .in("status", ["Aktiv", "Karenz"]),
     supabase.from("divisions").select("*").order("name"),