Add account hierarchy framework with migrations, RLS policies, and UI components

apps/web/app/[locale]/home/[account]/verband/hierarchy/page.tsx

@@ -0,0 +1,48 @@
+import { getSupabaseServerClient } from '@kit/supabase/server-client';
+import { createVerbandApi } from '@kit/verbandsverwaltung/api';
+import {
+  VerbandTabNavigation,
+  HierarchyTree,
+} from '@kit/verbandsverwaltung/components';
+
+import { AccountNotFound } from '~/components/account-not-found';
+import { CmsPageShell } from '~/components/cms-page-shell';
+
+interface PageProps {
+  params: Promise<{ account: string }>;
+}
+
+export default async function HierarchyPage({ params }: PageProps) {
+  const { account } = await params;
+  const client = getSupabaseServerClient();
+
+  const { data: acct } = await client
+    .from('accounts')
+    .select('id')
+    .eq('slug', account)
+    .single();
+
+  if (!acct) return <AccountNotFound />;
+
+  const api = createVerbandApi(client);
+
+  const [tree, availableAccounts] = await Promise.all([
+    api.getHierarchyTree(acct.id),
+    api.searchAvailableAccounts(acct.id),
+  ]);
+
+  return (
+    <CmsPageShell
+      account={account}
+      title="Verbandsverwaltung - Hierarchie"
+      description="Verwalten Sie die Organisationsstruktur Ihres Verbands"
+    >
+      <VerbandTabNavigation account={account} activeTab="hierarchy" />
+      <HierarchyTree
+        accountId={acct.id}
+        tree={tree}
+        availableAccounts={availableAccounts}
+      />
+    </CmsPageShell>
+  );
+}