feat: add landing page with beta signup + raise KB node limit to 100

Landing page at /landing with full marketing content: hero, features,
pricing, testimonials, and beta email signup form. Beta signups email
beta@resolutionflow.com via new public endpoint. Unauthenticated users
redirect to landing instead of login. Also raises KB Accelerator node
limit from 50 to 100 to accommodate dense troubleshooting articles.

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

frontend/src/router.tsx

@@ -13,6 +13,7 @@ import {
 } from '@/pages'
 
 // Public pages
+const LandingPage = lazy(() => import('@/pages/LandingPage'))
 const SharedSessionPage = lazy(() => import('@/pages/SharedSessionPage'))
 const SurveyPage = lazy(() => import('@/pages/SurveyPage'))
 const SurveyThankYouPage = lazy(() => import('@/pages/SurveyThankYouPage'))
@@ -78,6 +79,11 @@ function page(Component: React.LazyExoticComponent<React.ComponentType>) {
 }
 
 export const router = sentryCreateBrowserRouter([
+  {
+    path: '/landing',
+    element: page(LandingPage),
+    errorElement: <RouteError />,
+  },
   {
     path: '/login',
     element: <LoginPage />,