Full Changelog: 5.5.2...5.5.3

• feat: 網站背景支援隨機數組配置，可從多個背景中隨機選擇
• feat: 增加文章分頁封面配置 pagination_cover 選項
• improvement: 優化代碼高亮工具複製按鈕的位置計算和邊界檢查
• improvement: 優化 Pjax 載入，script 標籤新增 defer 屬性
• improvement: 優化相關文章算法，提升性能並改進排序邏輯
• improvement: 優化側邊欄歸檔和分類模塊的性能
• improvement: 改善 TOC 滾動檢測和位置計算
• improvement: 優化 Umami Analytics 數據處理邏輯
• fix: 修復代碼塊工具欄圖標對齊和樣式問題
• fix: 修復夜間模式下圖片亮度調整
• fix: 修復閱讀模式按鈕樣式和功能
• chore: 更新多個依賴套件版本（algolia, fancybox, katex, mermaid, waline 等）

• feat: add random background array support for website backgrounds
• feat: add pagination_cover option for post pagination covers
• improvement: optimize code highlight copy button positioning and boundary checks
• improvement: enhance Pjax loading with defer attribute on script tags
• improvement: optimize related posts algorithm for better performance and sorting
• improvement: improve aside archives and categories module performance
• improvement: enhance TOC scroll detection and position calculation
• improvement: optimize Umami Analytics data processing logic
• fix: resolve code block toolbar icon alignment and styling issues
• fix: adjust image brightness in dark mode
• fix: fix read mode button styling and functionality
• chore: update multiple dependency versions (algolia, fancybox, katex, mermaid, waline, etc.)