feat(knowledge): add short-term ask memory

backend/script/sql/aihr_knowledge_mysql8.sql

@@ -231,6 +231,22 @@ CREATE TABLE IF NOT EXISTS `aihr_knowledge_query_log` (
   KEY `idx_aihr_query_status` (`tenant_id`, `status`, `create_time`)
 ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci COMMENT='知识问答最小化审计日志';
 
+CREATE TABLE IF NOT EXISTS `aihr_knowledge_conversation` (
+  `id` bigint NOT NULL AUTO_INCREMENT COMMENT '主键',
+  `tenant_id` varchar(20) NOT NULL COMMENT '租户编号',
+  `app_id` bigint NOT NULL COMMENT '内部调用应用ID',
+  `user_id` bigint NOT NULL COMMENT '内部用户ID',
+  `conversation_id` varchar(64) NOT NULL COMMENT '客户端随机会话ID',
+  `version` bigint NOT NULL DEFAULT 0 COMMENT '乐观并发版本',
+  `context_json` json DEFAULT NULL COMMENT '最近六轮脱敏短期上下文',
+  `expires_time` datetime NOT NULL COMMENT '不活跃过期时间',
+  `create_time` datetime NOT NULL COMMENT '创建时间',
+  `update_time` datetime NOT NULL COMMENT '更新时间',
+  PRIMARY KEY (`id`),
+  UNIQUE KEY `uk_aihr_knowledge_conversation` (`tenant_id`, `app_id`, `user_id`, `conversation_id`),
+  KEY `idx_aihr_knowledge_conversation_expire` (`tenant_id`, `expires_time`)
+) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_0900_ai_ci COMMENT='知识问答短期会话';
+
 CREATE TABLE IF NOT EXISTS `aihr_knowledge_admin_audit` (
   `id` bigint NOT NULL AUTO_INCREMENT COMMENT '主键',
   `tenant_id` varchar(20) NOT NULL COMMENT '租户编号',