chore: v5.7.0

- Remove APlayer/Meting music player support
- Upgrade Artalk to 2.10.0 and add vote feature
- Cache plugins.yml to avoid re-rendering on every generate
- Add null safety for error_404 and highlight config
- Fix series date timestamp format
- Enhance shuoshuo mockPost compatibility and error handling
- Prevent scrollbar flicker when fancybox is open
- Update plugin versions (docsearch, katex, twikoo)
- Bump version to 5.7.0

scripts/events/404.js

@@ -6,7 +6,8 @@
 'use strict'
 
 hexo.extend.generator.register('404', function (locals) {
-  if (!hexo.theme.config.error_404.enable) return
+  const error404 = hexo.theme.config.error_404 || {}
+  if (!error404.enable) return
   return {
     path: '404.html',
     layout: ['page'],