feat(admin): kullanıcı yönetimi tablosu ve diyalogları (mock)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/app/(app)/admin/kullanicilar/page.tsx

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+import type { Metadata } from "next";
+import { PageHeader } from "@/components/page-header";
+import { UsersTable } from "@/features/admin-users/components/users-table";
+import { MOCK_ADMIN_USERS } from "@/features/admin-users/mock";
+import { MOCK_SESSION_USER } from "@/features/auth/mock";
+import { tr } from "@/i18n/tr";
+
+export const metadata: Metadata = { title: tr.adminUsers.title };
+
+export default function AdminUsersPage() {
+  // FAZ 3: const users = await listUsers() (Better Auth admin API)
+  return (
+    <>
+      <PageHeader title={tr.adminUsers.title} description={tr.adminUsers.description} />
+      <UsersTable initialUsers={MOCK_ADMIN_USERS} currentUserId={MOCK_SESSION_USER.id} />
+    </>
+  );
+}

src/app/(app)/admin/layout.tsx

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+import { notFound } from "next/navigation";
+import { MOCK_SESSION_USER } from "@/features/auth/mock";
+
+/**
+ * Yalnızca sistem admini. Admin olmayana 404 (sayfanın varlığını bile göstermez).
+ * FAZ 3: `await requireRole("admin")` (lib/dal.ts) — sunucu tarafı gerçek kontrol.
+ */
+export default function AdminLayout({ children }: { children: React.ReactNode }) {
+  if (MOCK_SESSION_USER.role !== "admin") notFound();
+  return children;
+}