feat(404): página custom con SSI de cPanel + htaccess con Options +Includes

- 404.shtml duplicado de 404.html con SSI embedded (REQUEST_URI, REMOTE_ADDR, HTTP_USER_AGENT, etc.)
- .htaccess actualizado: ErrorDocument 404 /404.shtml, Options +Includes, AddHandler server-parsed
- cPanel deshabilita Includes por default en cada VirtualHost, hay que activarlo en el .htaccess del usuario
- Verificado online: SSI procesa correctamente, URL/UA/IP visibles en la página

scripts/deploy.sh

@@ -20,6 +20,12 @@ cp /root/opencode/development/hostingdelsur.net/src/forms/api-htaccess "$DIST/ap
 # Copy root .htaccess (HTTPS forzado, security headers)
 cp /root/opencode/development/hostingdelsur.net/scripts/htaccess.conf "$DIST/.htaccess"
 
+# cPanel recognizes 404.shtml specifically (Server-Side Includes)
+# Astro generates 404.html — duplicate as .shtml for cPanel
+if [ -f "$DIST/404.html" ]; then
+  cp "$DIST/404.html" "$DIST/404.shtml"
+fi
+
 # rsync with --delete to mirror (preserva mwp/, .well-known/, etc.)
 rsync -avz --delete \
   --exclude='mwp' \