Revert "feat: serve content files via catch-all route, use content-relative cover images"

This reverts commit 8d582b6ae3.

next.config.ts

@@ -1,7 +1,9 @@
 import type { NextConfig } from 'next'
 
 const nextConfig: NextConfig = {
-  // Trailing slash for clean URLs
+  // Static export — generates out/ directory with plain HTML
+  output: 'export',
+  // Trailing slash for clean static URLs
   trailingSlash: true,
   // Images: unoptimized required for static export
   images: {