feat: 审批流程改为时间轴样式，增加审批人/抄送人标识

- 审批流程使用时间轴样式显示
- 增加"审批人"和"抄送人"标签
- 已审批节点显示审批人姓名和审批时间
- 未审批节点显示节点名称（人名）
- 当前审批节点高亮显示

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

frontend/src/pages/approval/detail.module.css

@@ -64,6 +64,9 @@
 .approverItem {
   padding: 8px 0;
   border-bottom: 1px solid #f0f0f0;
+  display: flex;
+  align-items: center;
+  gap: 8px;
 }
 
 .approverItem:last-child {
@@ -73,12 +76,15 @@
 .approverName {
   font-size: 15px;
   color: #333;
-  margin-bottom: 4px;
 }
 
 .approverType {
   font-size: 13px;
-  color: #999;
+  color: #fff;
+  background: #666;
+  padding: 2px 8px;
+  border-radius: 4px;
+  flex-shrink: 0;
 }
 
 .formData {
@@ -183,6 +189,20 @@
   align-items: center;
   justify-content: center;
   flex-shrink: 0;
+  background: #e8e8e8;
+  color: #999;
+  font-weight: 600;
+}
+
+.timelineDot.done {
+  background: #52c41a;
+  color: #fff;
+}
+
+.timelineDot.current {
+  background: #1890ff;
+  color: #fff;
+  box-shadow: 0 0 0 4px rgba(24, 144, 255, 0.2);
 }
 
 .timelineDotIcon {
@@ -197,6 +217,18 @@
   font-size: 15px;
   color: #333;
   margin-bottom: 4px;
+  display: flex;
+  align-items: center;
+  gap: 8px;
+}
+
+.timelineType {
+  font-size: 13px;
+  color: #fff;
+  background: #666;
+  padding: 2px 8px;
+  border-radius: 4px;
+  flex-shrink: 0;
 }
 
 .timelineName {