feat: 完成MES工位终端系统全量功能迭代

本次提交包含以下核心变更：
1. 新增按钮级权限控制框架与前端权限校验
2. 新增工位管理、工艺流程、巡检终端等核心业务模块
3. 完善用户体系，支持工位终端专属登录权限
4. 新增文件上传下载、报表查询等配套功能
5. 修复多系统兼容性与交互体验问题
6. 完成所有文档与配置项的规范化更新

bj_power_mes/internal/handler/upload.go

@@ -0,0 +1,71 @@
+package handler
+
+import (
+	"crypto/rand"
+	"encoding/hex"
+	"io"
+	"net/http"
+	"os"
+	"path/filepath"
+	"strings"
+	"time"
+)
+
+// saveUploadFile 保存上传文件（工艺图纸PDF / 巡检照片），返回生成的文件名
+func saveUploadFile(r *http.Request, field, dir string) (string, error) {
+	if err := os.MkdirAll(dir, 0o755); err != nil {
+		return "", err
+	}
+	file, header, err := r.FormFile(field)
+	if err != nil {
+		return "", err
+	}
+	defer file.Close()
+
+	ext := strings.ToLower(filepath.Ext(header.Filename))
+	if ext == "" {
+		ext = ".bin"
+	}
+	name := time.Now().Format("20060102150405") + "_" + randHex(6) + ext
+	dst, err := os.Create(filepath.Join(dir, name))
+	if err != nil {
+		return "", err
+	}
+	defer dst.Close()
+	if _, err := io.Copy(dst, file); err != nil {
+		return "", err
+	}
+	return name, nil
+}
+
+func randHex(n int) string {
+	b := make([]byte, n)
+	_, _ = rand.Read(b)
+	return hex.EncodeToString(b)[:n*2]
+}
+
+// serveUploadFile 下发上传目录中的文件（限制为单段文件名，防路径穿越）
+func serveUploadFile(w http.ResponseWriter, r *http.Request, dir, name string) {
+	name = strings.TrimSpace(filepath.Base(name))
+	if name == "" || name == "." || name == ".." || strings.Contains(name, "..") {
+		http.Error(w, "非法文件名", http.StatusBadRequest)
+		return
+	}
+	f, err := os.Open(filepath.Join(dir, name))
+	if err != nil {
+		http.Error(w, "文件不存在", http.StatusNotFound)
+		return
+	}
+	defer f.Close()
+	ct := "application/octet-stream"
+	switch {
+	case strings.HasSuffix(strings.ToLower(name), ".pdf"):
+		ct = "application/pdf"
+	case strings.HasSuffix(strings.ToLower(name), ".jpg"), strings.HasSuffix(strings.ToLower(name), ".jpeg"):
+		ct = "image/jpeg"
+	case strings.HasSuffix(strings.ToLower(name), ".png"):
+		ct = "image/png"
+	}
+	w.Header().Set("Content-Type", ct)
+	http.ServeContent(w, r, name, time.Time{}, f)
+}