支持项目编码访问单项目公示屏

需求：无需查询公示 Token，直接通过项目编码打开单项目公示页。

实现：规范化项目编码并按 code 查询，同时保留既有 Token 哈希查询；补充前后端及集成回归测试。

server/internal/httpapi/public.go

@@ -288,14 +288,27 @@ type displaySnapshotDTO struct {
 	LastUpdatedAt      time.Time         `json:"last_updated_at"`
 }
 
-func (s *Server) displaySnapshot(w http.ResponseWriter, r *http.Request) {
-	token := strings.TrimSpace(r.PathValue("token"))
-	if len(token) < 40 || len(token) > 128 {
-		writeError(w, &apiError{Status: http.StatusNotFound, Code: "DISPLAY_NOT_FOUND", Message: "公示屏绑定不存在"})
-		return
+func normalizeDisplayProjectCode(value string) (string, bool) {
+	code := strings.ToUpper(strings.TrimSpace(value))
+	if !projectCodePattern.MatchString(code) {
+		return "", false
 	}
+	return code, true
+}
+
+func (s *Server) displaySnapshot(w http.ResponseWriter, r *http.Request) {
+	identifier := strings.TrimSpace(r.PathValue("token"))
 	var project model.Project
-	err := s.db.WithContext(r.Context()).Where("display_token_hash = ?", security.HashToken(token)).First(&project).Error
+	var err error
+	if code, ok := normalizeDisplayProjectCode(identifier); ok {
+		err = s.db.WithContext(r.Context()).Where("code = ?", code).First(&project).Error
+	} else {
+		if len(identifier) < 40 || len(identifier) > 128 {
+			writeError(w, &apiError{Status: http.StatusNotFound, Code: "DISPLAY_NOT_FOUND", Message: "公示屏绑定不存在"})
+			return
+		}
+		err = s.db.WithContext(r.Context()).Where("display_token_hash = ?", security.HashToken(identifier)).First(&project).Error
+	}
 	if err != nil {
 		writeError(w, mapNotFound(err, "DISPLAY_NOT_FOUND", "公示屏绑定不存在"))
 		return