feat(hrm): 添加请假统计功能

- 在控制器中新增 /stats 接口用于获取请假统计数据
- 新增 HrmLeaveStatsVo 数据传输对象定义统计结构
- 在数据访问层添加多个统计查询方法，包括按类型、部门、月份统计
- 实现服务层统计业务逻辑，包括请假汇总、分类统计、员工状态统计
- 配置 MyBatis 映射文件实现各维度统计 SQL 查询
- 添加员工总数和请假中员工数的统计功能

fad-hrm/src/main/resources/mapper/HrmLeaveReqMapper.xml

@@ -149,4 +149,64 @@
         </if>
         ORDER BY l.create_time DESC
     </select>
+    <!-- 统计查询 -->
+    <select id="selectLeaveSummary" resultType="java.util.Map">
+        SELECT
+            COUNT(*) as totalRequests,
+            SUM(hours) as totalHours
+        FROM hrm_leave_req
+        WHERE del_flag = 0
+          AND status = 'approved'
+    </select>
+
+    <select id="selectLeaveByType" resultType="java.util.Map">
+        SELECT
+            leave_type as leaveType,
+            COUNT(*) as count,
+            SUM(hours) as totalHours
+        FROM hrm_leave_req
+        WHERE del_flag = 0
+          AND status = 'approved'
+        GROUP BY leave_type
+        ORDER BY totalHours DESC
+    </select>
+
+    <select id="selectLeaveByDept" resultType="java.util.Map">
+        SELECT
+            d.dept_name as deptName,
+            COUNT(l.biz_id) as count,
+            SUM(l.hours) as totalHours
+        FROM hrm_leave_req l
+            JOIN hrm_employee e ON l.emp_id = e.emp_id AND e.del_flag = 0
+            LEFT JOIN sys_dept d ON e.dept_id = d.dept_id AND d.del_flag = '0'
+        WHERE l.del_flag = 0
+          AND l.status = 'approved'
+        GROUP BY d.dept_id, d.dept_name
+        ORDER BY totalHours DESC
+    </select>
+
+    <select id="selectLeaveByMonth" resultType="java.util.Map">
+        SELECT
+            DATE_FORMAT(start_time, '%Y-%m') as month,
+            COUNT(*) as count,
+            SUM(hours) as totalHours
+        FROM hrm_leave_req
+        WHERE del_flag = 0
+          AND status = 'approved'
+          AND YEAR(start_time) = #{year}
+        GROUP BY DATE_FORMAT(start_time, '%Y-%m')
+        ORDER BY month
+    </select>
+
+    <select id="selectTotalEmployees" resultType="java.lang.Integer">
+        SELECT COUNT(*) FROM hrm_employee WHERE del_flag = 0 AND status = 'onboard'
+    </select>
+
+    <select id="selectLeavingEmployees" resultType="java.lang.Integer">
+        SELECT COUNT(DISTINCT l.emp_id)
+        FROM hrm_leave_req l
+        WHERE l.del_flag = 0
+          AND l.status = 'approved'
+          AND NOW() BETWEEN l.start_time AND l.end_time
+    </select>
 </mapper>