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/SlideOver.tsx

@@ -0,0 +1,55 @@
+"use client";
+
+import { X } from "lucide-react";
+import { useEffect, type ReactNode } from "react";
+
+type SlideOverProps = {
+  open: boolean;
+  onClose: () => void;
+  title: string;
+  subtitle?: string;
+  children: ReactNode;
+  footer?: ReactNode;
+};
+
+export function SlideOver({ open, onClose, title, subtitle, children, footer }: SlideOverProps) {
+  useEffect(() => {
+    if (!open) return;
+    const onKey = (e: KeyboardEvent) => {
+      if (e.key === "Escape") onClose();
+    };
+    window.addEventListener("keydown", onKey);
+    return () => window.removeEventListener("keydown", onKey);
+  }, [open, onClose]);
+
+  return (
+    <div className={`fixed inset-0 z-50 ${open ? "pointer-events-auto" : "pointer-events-none"}`} aria-hidden={!open}>
+      <div
+        className={`absolute inset-0 bg-black/40 transition-opacity ${open ? "opacity-100" : "opacity-0"}`}
+        onClick={onClose}
+      />
+      <div
+        className={`absolute right-0 top-0 flex h-full w-full max-w-md flex-col bg-white shadow-xl transition-transform duration-200 ${
+          open ? "translate-x-0" : "translate-x-full"
+        }`}
+      >
+        <div className="flex items-start justify-between border-b border-border px-6 py-4">
+          <div>
+            <h2 className="text-lg font-bold text-ink">{title}</h2>
+            {subtitle && <p className="text-sm text-ink-muted">{subtitle}</p>}
+          </div>
+          <button
+            type="button"
+            onClick={onClose}
+            aria-label="Schließen"
+            className="rounded p-1 text-ink-muted hover:bg-surface"
+          >
+            <X className="h-5 w-5" />
+          </button>
+        </div>
+        <div className="flex-1 overflow-y-auto px-6 py-4">{children}</div>
+        {footer && <div className="flex items-center justify-end gap-2 border-t border-border px-6 py-4">{footer}</div>}
+      </div>
+    </div>
+  );
+}