增加ai配置和ai广场功能

go/docs/sql/create_platform_ai_chat.sql

@@ -0,0 +1,25 @@
+-- 平台 AI Playground 会话与消息表
+CREATE TABLE IF NOT EXISTS `yz_platform_ai_chat_session` (
+  `id` bigint unsigned NOT NULL AUTO_INCREMENT,
+  `title` varchar(100) NOT NULL DEFAULT '' COMMENT '会话标题（首条用户消息摘要）',
+  `provider_id` bigint unsigned NOT NULL DEFAULT 0 COMMENT '服务商配置ID',
+  `model` varchar(100) NOT NULL DEFAULT '' COMMENT '模型ID',
+  `create_time` datetime NOT NULL,
+  `update_time` datetime NOT NULL,
+  `delete_time` datetime DEFAULT NULL,
+  PRIMARY KEY (`id`),
+  KEY `idx_delete_time` (`delete_time`),
+  KEY `idx_update_time` (`update_time`)
+) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COMMENT='平台AI会话';
+
+CREATE TABLE IF NOT EXISTS `yz_platform_ai_chat_message` (
+  `id` bigint unsigned NOT NULL AUTO_INCREMENT,
+  `session_id` bigint unsigned NOT NULL DEFAULT 0,
+  `role` varchar(20) NOT NULL DEFAULT '' COMMENT 'user/assistant/system',
+  `content` text COMMENT 'user存原始content JSON（可含附件）；assistant存纯文本',
+  `think` text COMMENT 'assistant思考过程',
+  `seq` int NOT NULL DEFAULT 0 COMMENT '消息序号',
+  `create_time` datetime NOT NULL,
+  PRIMARY KEY (`id`),
+  KEY `idx_session_seq` (`session_id`, `seq`)
+) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COMMENT='平台AI会话消息';