feat(bx): add occur_date column on reimburse detail

Store optional expense occurrence date (DATE, nullable) for each
reimburse line item.

Co-authored-by: Cursor <cursoragent@cursor.com>

docs/sql/shanxia2.0.sql

@@ -953,6 +953,7 @@ CREATE TABLE `bx_reimburse_detail` (
   `expense_id` varchar(64) NOT NULL COMMENT '费用项目ID',
   `expense_name` varchar(128) NOT NULL COMMENT '费用项目名称',
   `amount` decimal(14,2) NOT NULL COMMENT '报销金额',
+  `occur_date` date DEFAULT NULL COMMENT '费用发生日期',
   `tenant_no` varchar(64) NOT NULL DEFAULT 'shanxia2.0' COMMENT '租户编号',
   `order_num` int(11) DEFAULT NULL COMMENT '排序号(公共)',
   `remark` varchar(512) DEFAULT NULL COMMENT '备注',