fix: 修复http.FS过滤下划线开头文件导致404的问题

- 使用fs.ReadFile直接读取文件内容替代c.FileFromFS
- http.FileServer/http.FS默认过滤以_开头的文件
- 手动设置Content-Type确保正确的MIME类型
- 移除不再需要的net/http导入

backend/cmd/main.go

@@ -5,7 +5,6 @@ import (
 	"fmt"
 	"io/fs"
 	"log"
-	"net/http"
 	"net/url"
 	"os"
 	"strings"
@@ -283,16 +282,40 @@ func setupEmbeddedFrontend(r *gin.Engine) {
 
 		fullPath := "assets/" + decodedPath
 
-		f, err := distFS.Open(fullPath)
+		data, err := fs.ReadFile(distFS, fullPath)
 		if err != nil {
 			log.Printf("[Assets] File not found in embedded FS: %s, error: %v", fullPath, err)
 			c.Status(404)
 			return
 		}
-		f.Close()
 
+		contentType := "application/octet-stream"
+		switch {
+		case strings.HasSuffix(decodedPath, ".js"):
+			contentType = "application/javascript"
+		case strings.HasSuffix(decodedPath, ".css"):
+			contentType = "text/css"
+		case strings.HasSuffix(decodedPath, ".html"):
+			contentType = "text/html"
+		case strings.HasSuffix(decodedPath, ".json"):
+			contentType = "application/json"
+		case strings.HasSuffix(decodedPath, ".png"):
+			contentType = "image/png"
+		case strings.HasSuffix(decodedPath, ".jpg") || strings.HasSuffix(decodedPath, ".jpeg"):
+			contentType = "image/jpeg"
+		case strings.HasSuffix(decodedPath, ".svg"):
+			contentType = "image/svg+xml"
+		case strings.HasSuffix(decodedPath, ".ico"):
+			contentType = "image/x-icon"
+		case strings.HasSuffix(decodedPath, ".woff"):
+			contentType = "font/woff"
+		case strings.HasSuffix(decodedPath, ".woff2"):
+			contentType = "font/woff2"
+		}
+
+		c.Header("Content-Type", contentType)
 		c.Header("Cache-Control", "public, max-age=31536000, immutable")
-		c.FileFromFS(fullPath, http.FS(distFS))
+		c.Data(200, contentType, data)
 	})
 
 	r.NoRoute(func(c *gin.Context) {
@@ -306,9 +329,21 @@ func setupEmbeddedFrontend(r *gin.Engine) {
 		if err != nil {
 			decodedPath = path
 		}
-		if f, err := distFS.Open(decodedPath); err == nil {
-			f.Close()
-			c.FileFromFS(c.Request.URL.Path, http.FS(distFS))
+		if data, err := fs.ReadFile(distFS, decodedPath); err == nil {
+			contentType := "application/octet-stream"
+			switch {
+			case strings.HasSuffix(decodedPath, ".js"):
+				contentType = "application/javascript"
+			case strings.HasSuffix(decodedPath, ".css"):
+				contentType = "text/css"
+			case strings.HasSuffix(decodedPath, ".html"):
+				contentType = "text/html"
+			case strings.HasSuffix(decodedPath, ".png"):
+				contentType = "image/png"
+			case strings.HasSuffix(decodedPath, ".svg"):
+				contentType = "image/svg+xml"
+			}
+			c.Data(200, contentType, data)
 			return
 		}