Fix sign-in links and legacy JWT after Periscope rebrand.

/login 404ed from marketing CTAs; redirect to /sign-in and accept pinscope-local tokens plus dual-host CORS so login works on both hostnames.

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

frontend/next.config.ts

@@ -27,6 +27,12 @@ const nextConfig: NextConfig = {
       canvas: { browser: "" },
     },
   },
+  async redirects() {
+    return [
+      { source: "/login", destination: "/sign-in", permanent: false },
+      { source: "/register", destination: "/sign-up", permanent: false },
+    ];
+  },
   async headers() {
     return [
       {