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`).

components/employees/panels/DatenAendernPanel.tsx

@@ -9,7 +9,7 @@ import { useToast } from "@/components/ui/Toast";
 import { UN_COUNTRIES } from "@/lib/countries";
 import type { ContractType, Database, EmploymentType, GenderType } from "@/lib/supabase/types";
 
-type EmployeeRow = Database["public"]["Views"]["employees_directory"]["Row"];
+type EmployeeRow = Database["public"]["Tables"]["employees"]["Row"];
 
 export function DatenAendernPanel({ open, onClose, employee }: { open: boolean; onClose: () => void; employee: EmployeeRow }) {
   const { showToast } = useToast();