perf: 优化静态文件下载性能，支持断点续传

- 替换 Gin 默认 Static 为自定义处理器
- 支持 Range 请求头，实现断点续传
- 使用 1MB 大缓冲区，减少系统调用次数
- 添加 Accept-Ranges 和精确 Content-Length 响应头
- 设置正确的 MIME 类型映射

Co-Authored-By: Claude <noreply@anthropic.com>

backend/cmd/main.go

@@ -4,10 +4,14 @@ import (
 	"compress/gzip"
 	"embed"
 	"fmt"
+	"io"
 	"io/fs"
 	"log"
+	"net/http"
 	"net/url"
 	"os"
+	"path/filepath"
+	"strconv"
 	"strings"
 	"verification-platform-backend/internal/config"
 	"verification-platform-backend/internal/database"
@@ -238,7 +242,8 @@ func startServer() {
 		c.Next()
 	})
 
-	r.Static("/uploads", "uploads")
+	// 优化的静态文件服务，支持 Range 请求和断点续传
+	r.GET("/uploads/*filepath", handleOptimizedStaticFile)
 	router.SetupRoutes(r)
 	setupEmbeddedFrontend(r)
 
@@ -437,3 +442,195 @@ func (w *gzipResponseWriter) WriteString(s string) (int, error) {
 	}
 	return w.ResponseWriter.WriteString(s)
 }
+
+// 32KB 缓冲区用于文件传输
+// 1MB 缓冲区用于高速文件传输，适合 G 口带宽和大文件
+const fileBufferSize = 1024 * 1024
+
+// handleOptimizedStaticFile 优化的静态文件处理，支持 Range 请求和断点续传
+func handleOptimizedStaticFile(c *gin.Context) {
+	// 获取请求的文件路径
+	filepathParam := c.Param("filepath")
+	if filepathParam == "" {
+		c.Status(http.StatusBadRequest)
+		return
+	}
+
+	// 安全处理路径，防止目录遍历攻击
+	filepathParam = strings.TrimPrefix(filepathParam, "/")
+	fullPath := filepath.Join("uploads", filepathParam)
+
+	// 清理路径，防止 .. 攻击
+	cleanPath := filepath.Clean(fullPath)
+	if !strings.HasPrefix(cleanPath, "uploads"+string(os.PathSeparator)) && cleanPath != "uploads" {
+		c.Status(http.StatusForbidden)
+		return
+	}
+
+	// 打开文件
+	file, err := os.Open(cleanPath)
+	if err != nil {
+		if os.IsNotExist(err) {
+			c.Status(http.StatusNotFound)
+		} else {
+			c.Status(http.StatusInternalServerError)
+		}
+		return
+	}
+	defer file.Close()
+
+	// 获取文件信息
+	fileInfo, err := file.Stat()
+	if err != nil {
+		c.Status(http.StatusInternalServerError)
+		return
+	}
+
+	// 如果是目录，返回 404
+	if fileInfo.IsDir() {
+		c.Status(http.StatusNotFound)
+		return
+	}
+
+	// 获取文件大小
+	fileSize := fileInfo.Size()
+
+	// 设置响应头
+	c.Header("Accept-Ranges", "bytes")
+	c.Header("Cache-Control", "public, max-age=31536000, immutable")
+
+	// 获取 MIME 类型
+	ext := strings.ToLower(filepath.Ext(cleanPath))
+	if mimeType, ok := mimeTypes[ext]; ok {
+		c.Header("Content-Type", mimeType)
+	} else {
+		c.Header("Content-Type", "application/octet-stream")
+	}
+
+	// 处理 Range 请求（断点续传）
+	rangeHeader := c.GetHeader("Range")
+	if rangeHeader != "" {
+		// 解析 Range 头
+		// 格式: bytes=start-end 或 bytes=start-
+		rangeParts := strings.TrimPrefix(rangeHeader, "bytes=")
+		if rangeParts != rangeHeader {
+			// 解析范围
+			var start, end int64
+			if strings.Contains(rangeParts, "-") {
+				parts := strings.Split(rangeParts, "-")
+				if len(parts) == 2 {
+					if parts[0] != "" {
+						start, _ = strconv.ParseInt(parts[0], 10, 64)
+					}
+					if parts[1] != "" {
+						end, _ = strconv.ParseInt(parts[1], 10, 64)
+					} else {
+						end = fileSize - 1
+					}
+				}
+			}
+
+			// 验证范围
+			if start >= fileSize || start < 0 || end < start || end >= fileSize {
+				c.Header("Content-Range", fmt.Sprintf("bytes */%d", fileSize))
+				c.Status(http.StatusRequestedRangeNotSatisfiable)
+				return
+			}
+
+			// 设置部分内容响应
+			c.Header("Content-Range", fmt.Sprintf("bytes %d-%d/%d", start, end, fileSize))
+			c.Header("Content-Length", strconv.FormatInt(end-start+1, 10))
+			c.Status(http.StatusPartialContent)
+
+			// 定位到起始位置
+			file.Seek(start, io.SeekStart)
+
+			// 使用缓冲区传输
+			buf := make([]byte, fileBufferSize)
+			remaining := end - start + 1
+			for remaining > 0 {
+				toRead := int64(fileBufferSize)
+				if remaining < toRead {
+					toRead = remaining
+				}
+				n, err := file.Read(buf[:toRead])
+				if err != nil && err != io.EOF {
+					break
+				}
+				if n == 0 {
+					break
+				}
+				c.Writer.Write(buf[:n])
+				remaining -= int64(n)
+			}
+			return
+		}
+	}
+
+	// 普通请求，发送整个文件
+	c.Header("Content-Length", strconv.FormatInt(fileSize, 10))
+	c.Status(http.StatusOK)
+
+	// 使用缓冲区高效传输
+	buf := make([]byte, fileBufferSize)
+	_, err = io.CopyBuffer(c.Writer, file, buf)
+	if err != nil {
+		log.Printf("Error sending file %s: %v", cleanPath, err)
+	}
+}
+
+// mimeTypes 常见 MIME 类型映射
+var mimeTypes = map[string]string{
+	".zip":    "application/zip",
+	".exe":    "application/vnd.microsoft.windows.executable",
+	".dll":    "application/vnd.microsoft.windows.dll",
+	".apk":    "application/vnd.android.package-archive",
+	".ipa":    "application/vnd.apple.ipa",
+	".dmg":    "application/vnd.apple.dmg",
+	".pdf":    "application/pdf",
+	".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",
+	".mp4":    "video/mp4",
+	".mp3":    "audio/mpeg",
+	".wav":    "audio/wav",
+	".ogg":    "audio/ogg",
+	".flac":   "audio/flac",
+	".avi":    "video/x-msvideo",
+	".mkv":    "video/x-matroska",
+	".mov":    "video/quicktime",
+	".wmv":    "video/x-ms-wmv",
+	".jpg":    "image/jpeg",
+	".jpeg":   "image/jpeg",
+	".png":    "image/png",
+	".gif":    "image/gif",
+	".bmp":    "image/bmp",
+	".webp":   "image/webp",
+	".svg":    "image/svg+xml",
+	".ico":    "image/x-icon",
+	".html":   "text/html; charset=utf-8",
+	".htm":    "text/html; charset=utf-8",
+	".css":    "text/css; charset=utf-8",
+	".js":     "application/javascript; charset=utf-8",
+	".mjs":    "application/javascript; charset=utf-8",
+	".json":   "application/json; charset=utf-8",
+	".xml":    "application/xml; charset=utf-8",
+	".txt":    "text/plain; charset=utf-8",
+	".md":     "text/markdown; charset=utf-8",
+	".log":    "text/plain; charset=utf-8",
+	".csv":    "text/csv; charset=utf-8",
+	".tar":    "application/x-tar",
+	".gz":     "application/gzip",
+	".tgz":    "application/gzip",
+	".rar":    "application/vnd.rar",
+	".7z":     "application/x-7z-compressed",
+	".iso":    "application/x-iso9660-image",
+	".woff":   "font/woff",
+	".woff2":  "font/woff2",
+	".ttf":    "font/ttf",
+	".eot":    "application/vnd.ms-fontobject",
+	".otf":    "font/otf",
+}