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/ui/SegmentedControl.tsx

@@ -0,0 +1,28 @@
+"use client";
+
+type Option<T extends string> = { value: T; label: string };
+
+type SegmentedControlProps<T extends string> = {
+  value: T;
+  onChange: (value: T) => void;
+  options: Option<T>[];
+};
+
+export function SegmentedControl<T extends string>({ value, onChange, options }: SegmentedControlProps<T>) {
+  return (
+    <div className="inline-flex rounded bg-surface p-1">
+      {options.map((opt) => (
+        <button
+          key={opt.value}
+          type="button"
+          onClick={() => onChange(opt.value)}
+          className={`rounded px-3 py-1.5 text-sm font-semibold transition-colors ${
+            value === opt.value ? "bg-white text-brand-700 shadow-sm" : "text-ink-muted hover:text-ink"
+          }`}
+        >
+          {opt.label}
+        </button>
+      ))}
+    </div>
+  );
+}