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`).

lib/format.ts

@@ -4,11 +4,6 @@ const dateFormatter = new Intl.DateTimeFormat("de-AT", {
   year: "numeric",
 });
 
-const eurFormatter = new Intl.NumberFormat("de-AT", {
-  style: "currency",
-  currency: "EUR",
-});
-
 export function fmtDate(date: string | Date | null | undefined): string {
   if (!date) return "–";
   const d = typeof date === "string" ? new Date(date) : date;
@@ -16,11 +11,6 @@ export function fmtDate(date: string | Date | null | undefined): string {
   return dateFormatter.format(d);
 }
 
-export function fmtEUR(amount: number | null | undefined): string {
-  if (amount === null || amount === undefined) return "••• (ausgeblendet)";
-  return eurFormatter.format(amount);
-}
-
 export function initials(firstName: string, lastName: string): string {
   const a = firstName.trim().charAt(0).toUpperCase();
   const b = lastName.trim().charAt(0).toUpperCase();