refactor: move backend files to backend/ directory

Reorganize project structure:
- backend/cmd/openteam/ — entry point
- backend/internal/ — core packages
- backend/middleware/ — HTTP middleware
- backend/router/ — route setup
- backend/wire/ — dependency injection
- backend/pkg/ — shared utilities
- backend/go.mod, go.sum — Go module files

Updated Makefile to work from backend/ directory.
Removed old lowercase makefile.

backend/internal/cli/cli.go

@@ -0,0 +1,66 @@
+package cli
+
+import (
+	"encoding/json"
+	"fmt"
+	"log"
+	"opencatd-open/internal/store"
+	"os"
+	"strings"
+
+	"github.com/google/uuid"
+	"github.com/spf13/cobra"
+)
+
+var LoadCmd = &cobra.Command{
+	Use:   "load",
+	Short: "import user.json -> db",
+	Long:  "\nimport user.json -> db",
+	Run: func(cmd *cobra.Command, args []string) {
+		db := store.DB
+		var cont int64
+		if err := db.Model(&store.User{}).Count(&cont).Error; err != nil {
+			fmt.Println(err)
+			return
+		}
+		if cont == 0 {
+			fmt.Println("创建管理员之后再操作")
+			return
+		}
+		if _, err := os.Stat("./db/user.json"); os.IsNotExist(err) {
+			log.Fatalln("404! user.json is not found.")
+			return
+		}
+		file, err := os.Open("./db/user.json")
+		if err != nil {
+			fmt.Println("Error opening file:", err)
+			return
+		}
+		defer file.Close()
+
+		var usermap []map[string]string
+		if err := json.NewDecoder(file).Decode(&usermap); err != nil {
+			fmt.Println("解析文件失败:", err)
+			return
+		}
+		for _, um := range usermap {
+			name := um["username"]
+			if name == "" {
+				name = um["name"]
+			}
+			if name == "" {
+				fmt.Println("获取不到数据")
+				continue
+			}
+			_ = "sk-ot-" + strings.ReplaceAll(uuid.New().String(), "-", "")
+			fmt.Printf("Import user: %s\n", name)
+		}
+	},
+}
+
+var SaveCmd = &cobra.Command{
+	Use:   "save",
+	Short: "backup user info -> user.json",
+	Run: func(cmd *cobra.Command, args []string) {
+	},
+}