debug: 添加嵌入文件系统调试日志

- 启动时列出所有嵌入的assets文件
- 请求assets文件时添加文件查找日志

backend/cmd/main.go

@@ -256,6 +256,17 @@ func setupEmbeddedFrontend(r *gin.Engine) {
 		return
 	}
 
+	log.Printf("[Embed] Listing embedded files in assets/:")
+	fs.WalkDir(distFS, "assets", func(path string, d fs.DirEntry, err error) error {
+		if err != nil {
+			return err
+		}
+		if !d.IsDir() {
+			log.Printf("[Embed]   %s", path)
+		}
+		return nil
+	})
+
 	indexHTML, err := fs.ReadFile(distFS, "index.html")
 	if err != nil {
 		log.Printf("Warning: index.html not found in embedded dist")
@@ -269,8 +280,19 @@ func setupEmbeddedFrontend(r *gin.Engine) {
 		if err != nil {
 			decodedPath = filepath
 		}
+
+		fullPath := "assets/" + decodedPath
+
+		f, err := distFS.Open(fullPath)
+		if err != nil {
+			log.Printf("[Assets] File not found in embedded FS: %s, error: %v", fullPath, err)
+			c.Status(404)
+			return
+		}
+		f.Close()
+
 		c.Header("Cache-Control", "public, max-age=31536000, immutable")
-		c.FileFromFS("assets/"+decodedPath, http.FS(distFS))
+		c.FileFromFS(fullPath, http.FS(distFS))
 	})
 
 	r.NoRoute(func(c *gin.Context) {