feat: add AccountsList with Add Account form; proxy POST /accounts

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

apps/web/app/api/accounts/route.ts

@@ -4,3 +4,13 @@ export async function GET() {
   const res = await fetch(`${API_URL}/accounts`, { cache: 'no-store' });
   return Response.json(await res.json(), { status: res.status });
 }
+
+export async function POST(req: Request) {
+  const body = await req.json();
+  const res = await fetch(`${API_URL}/accounts`, {
+    method: 'POST',
+    headers: { 'Content-Type': 'application/json' },
+    body: JSON.stringify(body),
+  });
+  return Response.json(await res.json(), { status: res.status });
+}