feat(oa): add resignation kit with last_work_day writeback on approval

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

docs/sql/sys_user_last_work_day.sql

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+-- docs/sql/sys_user_last_work_day.sql
+-- 用户表补齐最后工作日（离职套件主数据）
+ALTER TABLE `sys_user`
+  ADD COLUMN `last_work_day` date DEFAULT NULL COMMENT '最后工作日' AFTER `probation_months`;