优化：代码质量提升，修复重复逻辑和语法高亮支持

- 简化计算属性，删除重复代码
- 优化文件扩展名获取逻辑
- 新增文件工具函数库 fileHelpers.js
- 增强 CodeEditor 语法高亮（支持 30+ 语言）
- 修复 Office 文档文件服务器访问权限
- 添加特殊文件名支持（Dockerfile、Makefile 等）

internal/filesystem/config.go

@@ -276,7 +276,13 @@ func getAllowedExtensions() map[string]bool {
 		".wav": true,
 		".ogg": true,
 		// 文档
-		".pdf": true,
+		".pdf":  true,
+		".doc":  true,
+		".docx": true,
+		".xls":  true,
+		".xlsx": true,
+		".ppt":  true,
+		".pptx": true,
 		// 文本
 		".txt": true,
 		".md":  true,
@@ -346,10 +352,20 @@ func getMIMETypeMapping() map[string]string {
 		".wav":  "audio/wav",
 		".ogg":  "audio/ogg",
 		".pdf":  "application/pdf",
+		// Office 文档
+		".doc":  "application/msword",
+		".docx": "application/vnd.openxmlformats-officedocument.wordprocessingml.document",
+		".xls":  "application/vnd.ms-excel",
+		".xlsx": "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet",
+		".ppt":  "application/vnd.ms-powerpoint",
+		".pptx": "application/vnd.openxmlformats-officedocument.presentationml.presentation",
+		// 文本
 		".txt":  "text/plain; charset=utf-8",
 		".html": "text/html; charset=utf-8",
 		".css":  "text/css",
 		".js":   "application/javascript",
 		".json": "application/json",
+		".xml":  "application/xml",
+		".md":   "text/markdown",
 	}
 }