chore: 后端首次基线提交

运行必须源码：app/(controller/model/service/middleware/lib/utils/validate/router)、config/、database/(migrations/seeders/sql)、启动脚本、app/public/templates 模板。
已忽略运行非必须：node_modules/、logs/、run/、app/public 运行时上传数据、.env*、构建/缓存产物。

seed-carousel.js

@@ -0,0 +1,40 @@
+const { Sequelize } = require('./node_modules/sequelize');
+const sequelize = new Sequelize('competition_db', 'root', '74191221', {
+  host: 'localhost', port: 3306, dialect: 'mysql',
+  logging: false
+});
+
+(async () => {
+  try {
+    await sequelize.authenticate();
+    console.log('DB connected');
+
+    // MariaDB 5.5 compatible: only one TIMESTAMP can have DEFAULT CURRENT_TIMESTAMP
+    await sequelize.query(`
+      CREATE TABLE IF NOT EXISTS carousel (
+        id INT UNSIGNED NOT NULL AUTO_INCREMENT,
+        image_url VARCHAR(500) NOT NULL,
+        sort_order INT NOT NULL DEFAULT 0,
+        link_url VARCHAR(500) NULL,
+        enabled TINYINT(1) NOT NULL DEFAULT 1,
+        created_at DATETIME NOT NULL,
+        updated_at DATETIME NOT NULL,
+        PRIMARY KEY (id),
+        KEY idx_sort_order (sort_order),
+        KEY idx_enabled (enabled)
+      ) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci
+    `);
+
+    const [rows] = await sequelize.query('SELECT COUNT(*) as cnt FROM carousel');
+    console.log('Existing:', rows[0].cnt);
+
+    if (rows[0].cnt === 0) {
+      await sequelize.query("INSERT INTO carousel (image_url, sort_order, enabled, created_at, updated_at) VALUES ('https://images.unsplash.com/photo-1446776811953-b23d57bd21aa?w=1200', 1, 1, NOW(), NOW())");
+      await sequelize.query("INSERT INTO carousel (image_url, sort_order, enabled, created_at, updated_at) VALUES ('https://images.unsplash.com/photo-1451187580459-43490279c0fa?w=1200', 2, 1, NOW(), NOW())");
+      await sequelize.query("INSERT INTO carousel (image_url, sort_order, enabled, created_at, updated_at) VALUES ('https://images.unsplash.com/photo-1614728263952-84ea256f9679?w=1200', 3, 1, NOW(), NOW())");
+      console.log('Inserted 3 carousel slides');
+    }
+    console.log('Done');
+  } catch(e) { console.error(e.message); }
+  finally { await sequelize.close(); }
+})();