Upgrade to Next.js 16, enable SSR, update packages

- Upgrade all packages to latest versions
- Enable SSR (dynamic = 'force-dynamic') for all pages
- Update PostCSS config for Tailwind CSS v4 (@tailwindcss/postcss)
- Fix Edge-compatible CSRF token generation (Web Crypto API)
- Remove deprecated eslint config from next.config.ts

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

next.config.ts

@@ -10,10 +10,7 @@ const nextConfig: NextConfig = {
   // Enable React strict mode for better error detection
   reactStrictMode: true,
 
-  // Temporarily ignore ESLint and TypeScript during build (pre-existing issues)
-  eslint: {
-    ignoreDuringBuilds: true,
-  },
+  // Temporarily ignore TypeScript during build (pre-existing issues)
   typescript: {
     ignoreBuildErrors: true,
   },