chore(init): 初始化解忧商行项目并完成 Phase 0 基座

backend/migrations/000009_admin_notifications.sql

@@ -0,0 +1,23 @@
+-- +goose Up
+-- +goose StatementBegin
+
+CREATE TABLE IF NOT EXISTS admin_notifications (
+  id BIGINT UNSIGNED PRIMARY KEY AUTO_INCREMENT,
+  admin_user_id BIGINT UNSIGNED NOT NULL COMMENT '接收管理员ID',
+  type VARCHAR(32) NOT NULL COMMENT '通知类型: system系统, chat聊天等',
+  title VARCHAR(128) NOT NULL COMMENT '通知标题',
+  content TEXT NULL COMMENT '通知内容',
+  is_read TINYINT(1) NOT NULL DEFAULT 0 COMMENT '是否已读',
+  created_at DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP,
+  updated_at DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
+  KEY idx_admin_notifications_user_read_created (admin_user_id, is_read, created_at)
+) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci COMMENT='管理员通知消息表';
+
+-- +goose StatementEnd
+
+-- +goose Down
+-- +goose StatementBegin
+
+DROP TABLE IF EXISTS admin_notifications;
+
+-- +goose StatementEnd