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/Avatar.tsx

@@ -0,0 +1,27 @@
+import { avatarColorFor } from "@/lib/colors";
+import { initials } from "@/lib/format";
+
+type AvatarProps = {
+  firstName: string;
+  lastName: string;
+  color?: string | null;
+  size?: "sm" | "md" | "lg";
+};
+
+const SIZE_CLASSES: Record<NonNullable<AvatarProps["size"]>, string> = {
+  sm: "h-7 w-7 text-xs",
+  md: "h-9 w-9 text-sm",
+  lg: "h-14 w-14 text-lg",
+};
+
+export function Avatar({ firstName, lastName, color, size = "md" }: AvatarProps) {
+  const bg = color ?? avatarColorFor(`${firstName}${lastName}`);
+  return (
+    <span
+      className={`inline-flex shrink-0 items-center justify-center rounded-full font-bold text-white ${SIZE_CLASSES[size]}`}
+      style={{ backgroundColor: bg }}
+    >
+      {initials(firstName, lastName)}
+    </span>
+  );
+}