chore: release v5.5.3

- Bump version from 5.5.3-b2 to 5.5.3 in package.json
- Update third-party dependencies:
  * algolia_search: 5.43.0 -> 5.46.0
  * docsearch: 4.3.1 -> 4.3.2
  * fancybox: 6.1.4 -> 6.1.7
  * katex: 0.16.25 -> 0.16.27
  * mermaid: 11.12.1 -> 11.12.2
  * waline: 3.7.1 -> 3.8.0

perf: optimize JavaScript performance
- Add defer attribute to script tags in pjax and prismjs
- Improve DOM content loading timing in pjax
- Optimize utilities with better throttle implementation
- Cache header positions for TOC performance
- Optimize related posts generation with Maps
- Improve archive helpers performance

fix: improve error handling and UI fixes
- Replace process.exit with proper error throwing
- Fix tooltip positioning with boundary checks
- Add btn-effects to readmode exit button
- Fix element height calculation for hidden elements
- Improve image filters in dark mode (brightness .88, contrast .95)

style: code improvements and consistency
- Refactor random cover generation with generator pattern
- Optimize data processing in helpers
- Clean up unused functions and improve code structure
- Fix Chinese translation: 页 -> 頁

source/css/_mode/readmode.styl

@@ -42,6 +42,7 @@ if hexo-config('readmode')
       font-size: 16px
       transition: background .3s
       addBorderRadius(8)
+      @extend .btn-effects
 
       +maxWidth768()
         top: initial