✨ 异常处置跟进支持上传附件

跟进记录新增 attachments_json 列，存 [{name, url}] 形式的 JSON 数组。
跟进说明与附件至少填其一即可：只传附件时，follow_content 列为 NOT NULL，
故写入固定文案「已上传跟进附件」，列表按该文案展示。

建表脚本补 COLLATE：原先只写 CHARSET，落到 MySQL 8 服务器默认排序规则，
与库中实际的 utf8mb4_0900_ai_ci 不一致。

blade-service/blade-transport/src/main/java/org/springblade/transport/service/impl/ExceptionDisposalServiceImpl.java

@@ -267,23 +267,30 @@ public class ExceptionDisposalServiceImpl
 		if (request == null || request.getId() == null) {
 			throw new ServiceException("请选择需要跟进的异常");
 		}
-		if (Func.isBlank(request.getFollowContent())) {
-			throw new ServiceException("请填写跟进说明");
+		boolean hasAttachments = Func.isNotBlank(request.getAttachmentsJson());
+		if (Func.isBlank(request.getFollowContent()) && !hasAttachments) {
+			throw new ServiceException("请填写跟进说明或上传附件");
 		}
-		if (request.getFollowContent().length() > 500) {
+		if (Func.isNotBlank(request.getFollowContent()) && request.getFollowContent().length() > 500) {
 			throw new ServiceException("跟进说明不能超过500字");
 		}
 		ExceptionDisposal disposal = getExisting(request.getId());
 		if (STATUS_COMPLETED.equals(disposal.getDisposalStatus())) {
 			throw new ServiceException("已完成的异常不允许继续跟进");
 		}
+		// 上传了附件但没写说明时，跟进说明留空，列表按附件回退展示
+		String followContent = Func.isBlank(request.getFollowContent())
+			? null
+			: request.getFollowContent();
 		disposal.setDisposalStatus(STATUS_PROCESSING);
-		disposal.setLatestFollowContent(request.getFollowContent());
+		disposal.setLatestFollowContent(Func.isBlank(followContent) ? "已上传跟进附件" : followContent);
 		updateById(disposal);
 
 		ExceptionDisposalFollowRecord record = new ExceptionDisposalFollowRecord();
 		record.setDisposalId(disposal.getId());
-		record.setFollowContent(request.getFollowContent());
+		// follow_content 列为 NOT NULL
+		record.setFollowContent(Func.isBlank(followContent) ? "已上传跟进附件" : followContent);
+		record.setAttachmentsJson(hasAttachments ? request.getAttachmentsJson() : null);
 		record.setFollowUser(AuthUtil.getUserId());
 		record.setFollowUserName(UserCache.getUserRealName(AuthUtil.getUserId()));
 		record.setFollowTime(LocalDateTime.now());