upgrade: Migrate to Vue 3

[KapilSachdev]

• Replaced Element UI with Element Plus.
• Updated 'highlight', 'lazyload', and 'mark' Vue directives.
• Added Prettier for code consistency across echarts project.
• Removed unused 'vue-text-highlight'.
• Removed container creation code (previously used with appendChild), as Vue 3 does not replace the mount element.
• Temporarily pinned Vue and Element Plus versions to those available from lib.baomitu.com (for consistency, rather than the official latest).