feat: AI改写功能集成角色数据 + UI优化

- 新增story_characters表和seed_characters.sql种子数据(27个角色)
- AI改写/续写功能注入角色信息(性别/年龄/外貌/性格)
- 首页UI下移避让微信退出按钮
- 个人中心页面布局重构

server/sql/schema.sql

@@ -176,3 +176,41 @@ CREATE TABLE IF NOT EXISTS `play_records` (
   CONSTRAINT `play_records_ibfk_1` FOREIGN KEY (`user_id`) REFERENCES `users` (`id`) ON DELETE CASCADE,
   CONSTRAINT `play_records_ibfk_2` FOREIGN KEY (`story_id`) REFERENCES `stories` (`id`) ON DELETE CASCADE
 ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COMMENT='游玩记录表';
+
+-- ============================================
+-- 9. 故事角色表
+-- ============================================
+CREATE TABLE IF NOT EXISTS `story_characters` (
+  `id` INT NOT NULL AUTO_INCREMENT,
+  `story_id` INT NOT NULL COMMENT '所属故事ID',
+  `name` VARCHAR(50) NOT NULL COMMENT '角色名称',
+  `role_type` VARCHAR(20) DEFAULT 'supporting' COMMENT '角色类型: protagonist/antagonist/supporting',
+  `gender` VARCHAR(10) DEFAULT '' COMMENT '性别: male/female/unknown',
+  `age_range` VARCHAR(20) DEFAULT '' COMMENT '年龄段: child/teen/young/middle/old',
+  `appearance` TEXT COMMENT '外貌描述（用于生成图片）',
+  `personality` TEXT COMMENT '性格描述',
+  `background` TEXT COMMENT '背景故事',
+  `avatar_prompt` TEXT COMMENT 'AI绘图提示词',
+  `avatar_url` VARCHAR(500) DEFAULT '' COMMENT '角色头像URL',
+  `created_at` TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
+  `updated_at` TIMESTAMP DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
+  PRIMARY KEY (`id`),
+  KEY `idx_story_id` (`story_id`),
+  CONSTRAINT `story_characters_ibfk_1` FOREIGN KEY (`story_id`) REFERENCES `stories` (`id`) ON DELETE CASCADE
+) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COMMENT='故事角色表';
+
+-- ============================================
+-- 10. 节点角色关联表
+-- ============================================
+CREATE TABLE IF NOT EXISTS `node_characters` (
+  `id` INT NOT NULL AUTO_INCREMENT,
+  `story_id` INT NOT NULL COMMENT '故事ID',
+  `node_key` VARCHAR(50) NOT NULL COMMENT '节点key',
+  `character_id` INT NOT NULL COMMENT '角色ID',
+  `is_speaker` TINYINT(1) DEFAULT 0 COMMENT '是否为该节点说话者',
+  `emotion` VARCHAR(30) DEFAULT 'neutral' COMMENT '该节点情绪: happy/sad/angry/neutral等',
+  PRIMARY KEY (`id`),
+  KEY `idx_story_node` (`story_id`, `node_key`),
+  KEY `idx_character` (`character_id`),
+  CONSTRAINT `node_characters_ibfk_1` FOREIGN KEY (`character_id`) REFERENCES `story_characters` (`id`) ON DELETE CASCADE
+) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COMMENT='节点角色关联表';