Phase 1: project foundation for Alpenwerk HR

Scaffolds the Next.js 16 / TypeScript strict / Tailwind v3 app per
NEXTJS_REBUILD_SUPERPROMPT.md, and implements the Foundation slice from
the Phase 1 plan:

- Corrected Supabase schema (supabase/schema.sql): org units, employees,
  history, positions, hire drafts, saved reports, audit log, reorg
  scenarios, role-based profiles, salary-masking view, RLS policies,
  auto-derivation triggers, position-number generator.
- Seed script (supabase/seed.ts): ~800 realistic Austrian employees across
  9 divisions / 16 departments / 35 teams, history, 8 open positions, and
  hr_admin/manager test accounts.
- Supabase clients (lib/supabase/*), design tokens (tailwind.config.ts),
  format/color helpers (lib/format.ts, lib/colors.ts).
- Shared UI kit (components/ui): Avatar, StatusChip, Toast, Modal,
  SlideOver, SegmentedControl, Lookup.
- Auth (login page, Server Actions) and proxy.ts (Next 16's replacement
  for middleware) guarding the authenticated route group.
- Shell (Sidebar, Topbar, NewHireButton stub) and the Dashboard page,
  reading live data via employees_directory.

Employees list/detail, hire wizard, action panels, org chart, positions,
reports, and audit log are deferred to later phases per the plan.

components/shell/NewHireButton.tsx

@@ -0,0 +1,20 @@
+"use client";
+
+import { Plus } from "lucide-react";
+import { useToast } from "@/components/ui/Toast";
+
+// Stub for Phase 1: the real 4-step hire wizard (§4.4) ships in a later phase.
+export function NewHireButton() {
+  const { showToast } = useToast();
+
+  return (
+    <button
+      type="button"
+      onClick={() => showToast("Der Neueinstellungs-Assistent folgt in einer späteren Ausbaustufe.", "info")}
+      className="flex items-center gap-1.5 rounded bg-brand-500 px-3 py-1.5 text-sm font-semibold text-white hover:bg-brand-600"
+    >
+      <Plus className="h-4 w-4" />
+      Neueinstellung
+    </button>
+  );
+}