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/ui/CountryPicker.tsx

@@ -14,10 +14,18 @@ type CountryPickerProps = {
 // value, not an object with its own detail fields.
 export function CountryPicker({ value, onChange, countries, placeholder = "Land suchen…" }: CountryPickerProps) {
   const [query, setQuery] = useState(value);
+  const [prevValue, setPrevValue] = useState(value);
   const [open, setOpen] = useState(false);
   const containerRef = useRef<HTMLDivElement>(null);
 
-  useEffect(() => setQuery(value), [value]);
+  // Re-sync the local draft text when `value` changes externally (e.g. the
+  // surrounding form loads a different employee). Adjusting state directly
+  // during render — rather than in an effect — avoids an extra render pass
+  // and the synchronous setState-in-effect this used to do.
+  if (value !== prevValue) {
+    setPrevValue(value);
+    setQuery(value);
+  }
 
   useEffect(() => {
     function onClickOutside(e: MouseEvent) {