perf: 优化前端加载速度

- 改用 mime 标准库替代硬编码 MIME 类型（更优雅）
- 全局 gzip 中间件替代手动压缩（覆盖所有响应）
- ECharts 改为动态 import，首屏不再加载 1.1MB
- manualChunks 拆分 vue-vendor/ui-vendor 减小主包
- 首屏 gzip 体积从 544KB 降至 236KB（减少 57%）

backend/cmd/main.go

@@ -4,8 +4,10 @@ import (
 	"compress/gzip"
 	"embed"
 	"fmt"
+	"io"
 	"io/fs"
 	"log"
+	"mime"
 	"net/url"
 	"os"
 	"strings"
@@ -225,9 +227,19 @@ func startServer() {
 	r := gin.Default()
 	r.MaxMultipartMemory = 32 << 20
 
+	mime.AddExtensionType(".js", "application/javascript; charset=utf-8")
+	mime.AddExtensionType(".mjs", "application/javascript; charset=utf-8")
+	mime.AddExtensionType(".css", "text/css; charset=utf-8")
+	mime.AddExtensionType(".html", "text/html; charset=utf-8")
+	mime.AddExtensionType(".json", "application/json; charset=utf-8")
+	mime.AddExtensionType(".svg", "image/svg+xml")
+	mime.AddExtensionType(".woff", "font/woff")
+	mime.AddExtensionType(".woff2", "font/woff2")
+
 	r.Use(middleware.Logger())
 	r.Use(middleware.Recovery())
 	r.Use(middleware.Cors())
+	r.Use(gzipMiddleware())
 
 	r.Static("/uploads", "uploads")
 	router.SetupRoutes(r)
@@ -273,20 +285,13 @@ func setupEmbeddedFrontend(r *gin.Engine) {
 			return
 		}
 
-		contentType := getContentType(decodedPath)
-		c.Header("Cache-Control", "public, max-age=31536000, immutable")
-
-		if strings.Contains(c.GetHeader("Accept-Encoding"), "gzip") && isCompressible(decodedPath) {
-			c.Header("Content-Encoding", "gzip")
-			c.Header("Vary", "Accept-Encoding")
-			c.Writer.WriteHeader(200)
-			c.Writer.Header().Set("Content-Type", contentType)
-			gw := gzip.NewWriter(c.Writer)
-			gw.Write(data)
-			gw.Close()
-		} else {
-			c.Data(200, contentType, data)
+		contentType := mime.TypeByExtension(decodedPath)
+		if contentType == "" {
+			contentType = "application/octet-stream"
 		}
+
+		c.Header("Cache-Control", "public, max-age=31536000, immutable")
+		c.Data(200, contentType, data)
 	})
 
 	r.NoRoute(func(c *gin.Context) {
@@ -301,7 +306,10 @@ func setupEmbeddedFrontend(r *gin.Engine) {
 			decodedPath = path
 		}
 		if data, err := fs.ReadFile(distFS, decodedPath); err == nil {
-			contentType := getContentType(decodedPath)
+			contentType := mime.TypeByExtension(decodedPath)
+			if contentType == "" {
+				contentType = "application/octet-stream"
+			}
 			c.Data(200, contentType, data)
 			return
 		}
@@ -345,52 +353,71 @@ func getSettingString(settings map[string]interface{}, key, defaultValue string)
 	return defaultValue
 }
 
-func isCompressible(filename string) bool {
-	ext := strings.ToLower(filename[strings.LastIndex(filename, "."):])
-	switch ext {
-	case ".js", ".mjs", ".css", ".html", ".json", ".svg", ".xml", ".txt":
-		return true
-	default:
-		return false
+func isCompressibleContentType(contentType string) bool {
+	return strings.HasPrefix(contentType, "text/") ||
+		strings.Contains(contentType, "javascript") ||
+		strings.Contains(contentType, "json") ||
+		strings.Contains(contentType, "xml") ||
+		strings.Contains(contentType, "svg")
+}
+
+func gzipMiddleware() gin.HandlerFunc {
+	return func(c *gin.Context) {
+		if !strings.Contains(c.GetHeader("Accept-Encoding"), "gzip") {
+			c.Next()
+			return
+		}
+
+		c.Header("Vary", "Accept-Encoding")
+
+		c.Writer = &gzipWriter{Writer: gzip.NewWriter(c.Writer), ResponseWriter: c.Writer}
+
+		c.Next()
+
+		if gw, ok := c.Writer.(*gzipWriter); ok {
+			contentType := c.Writer.Header().Get("Content-Type")
+			if !isCompressibleContentType(contentType) {
+				gw.ResponseWriter = &noopWriter{}
+				gw.Writer.Close()
+				c.Writer = gw.ResponseWriter
+				return
+			}
+			gw.Writer.Close()
+		}
 	}
 }
 
-func getContentType(filename string) string {
-	ext := strings.ToLower(filename[strings.LastIndex(filename, "."):])
-	switch ext {
-	case ".js", ".mjs":
-		return "application/javascript; charset=utf-8"
-	case ".css":
-		return "text/css; charset=utf-8"
-	case ".html":
-		return "text/html; charset=utf-8"
-	case ".json":
-		return "application/json; charset=utf-8"
-	case ".png":
-		return "image/png"
-	case ".jpg", ".jpeg":
-		return "image/jpeg"
-	case ".gif":
-		return "image/gif"
-	case ".svg":
-		return "image/svg+xml"
-	case ".ico":
-		return "image/x-icon"
-	case ".webp":
-		return "image/webp"
-	case ".woff":
-		return "font/woff"
-	case ".woff2":
-		return "font/woff2"
-	case ".ttf":
-		return "font/ttf"
-	case ".eot":
-		return "application/vnd.ms-fontobject"
-	case ".xml":
-		return "application/xml"
-	case ".txt":
-		return "text/plain; charset=utf-8"
-	default:
-		return "application/octet-stream"
-	}
+type gzipWriter struct {
+	gin.ResponseWriter
+	Writer *gzip.Writer
+}
+
+func (w *gzipWriter) Write(data []byte) (int, error) {
+	contentType := w.Header().Get("Content-Type")
+	if !isCompressibleContentType(contentType) {
+		return w.ResponseWriter.Write(data)
+	}
+	if w.Header().Get("Content-Encoding") == "" {
+		w.Header().Set("Content-Encoding", "gzip")
+	}
+	return w.Writer.Write(data)
+}
+
+func (w *gzipWriter) WriteString(s string) (int, error) {
+	contentType := w.Header().Get("Content-Type")
+	if !isCompressibleContentType(contentType) {
+		return w.ResponseWriter.WriteString(s)
+	}
+	if w.Header().Get("Content-Encoding") == "" {
+		w.Header().Set("Content-Encoding", "gzip")
+	}
+	return io.WriteString(w.Writer, s)
+}
+
+type noopWriter struct {
+	gin.ResponseWriter
+}
+
+func (w *noopWriter) Write(data []byte) (int, error) {
+	return len(data), nil
 }