Add login gate, calculation history, and AI markdown download.

Co-authored-by: Cursor <cursoragent@cursor.com>

middleware.ts

@@ -0,0 +1,38 @@
+import { NextResponse } from "next/server";
+import type { NextRequest } from "next/server";
+import { isAuthEnabled } from "@/lib/auth/config";
+import { SESSION_COOKIE, verifySessionToken } from "@/lib/auth/session";
+
+const PROTECTED_PREFIXES = ["/liuyao", "/bazi", "/combined", "/history"];
+
+export async function middleware(request: NextRequest) {
+  if (!isAuthEnabled()) {
+    return NextResponse.next();
+  }
+
+  const { pathname } = request.nextUrl;
+  const needsAuth =
+    PROTECTED_PREFIXES.some((p) => pathname === p || pathname.startsWith(`${p}/`)) ||
+    pathname.startsWith("/api/ai");
+
+  if (!needsAuth) {
+    return NextResponse.next();
+  }
+
+  const token = request.cookies.get(SESSION_COOKIE)?.value;
+  if (token && (await verifySessionToken(token))) {
+    return NextResponse.next();
+  }
+
+  if (pathname.startsWith("/api/")) {
+    return NextResponse.json({ error: "请先登录" }, { status: 401 });
+  }
+
+  const loginUrl = new URL("/login", request.url);
+  loginUrl.searchParams.set("next", pathname);
+  return NextResponse.redirect(loginUrl);
+}
+
+export const config = {
+  matcher: ["/liuyao/:path*", "/bazi/:path*", "/combined/:path*", "/history/:path*", "/api/ai"],
+};