refactor(docs): move sidebar styles to css file and remove cache busting

Clean up styles by moving them from config to dedicated CSS file
Remove unnecessary cache busting parameter from style import

docs/.vitepress/theme/index.js

@@ -4,7 +4,7 @@ import 'viewerjs/dist/viewer.css'
 import TypeIt from 'typeit'
 import { onMounted, watch, nextTick } from 'vue'
 import { useRoute, useData } from 'vitepress'
-import './style.css?v=20260112' // 强制刷新缓存
+import './style.css'
 
 export default {
   extends: DefaultTheme,