feat: Add Cross-Domain Job Fair and Alliance City Management

- Implemented AppOutdoorFairController for outdoor job fair public H5 interfaces.
- Created CrossCityAllianceController for managing cross-domain alliance cities.
- Added CrossCityAlliance domain model and corresponding service and mapper.
- Developed CrossDomainJobVO for aggregating job data across job fairs.
- Created SQL scripts for initializing the cross-city alliance table and modifying the public job fair schema.
- Added migration script for backing up and restoring the HighGo database schema.

ruoyi-bussiness/src/main/java/com/ruoyi/cms/mapper/CrossCityAllianceMapper.java

@@ -0,0 +1,11 @@
+package com.ruoyi.cms.mapper;
+
+import com.baomidou.mybatisplus.core.mapper.BaseMapper;
+import com.ruoyi.cms.domain.CrossCityAlliance;
+
+/**
+ * 跨域联合招聘会-联盟城市 Mapper。
+ */
+public interface CrossCityAllianceMapper extends BaseMapper<CrossCityAlliance>
+{
+}