feat: 初始化数据库结构，包括用户、OAuth账户、账户、账本、分类、标签和交易等表。

database/sql/schema.sql

@@ -1,9 +1,3 @@
--- Database Schema for Accounting App
--- Generated based on GORM models
-
-CREATE DATABASE IF NOT EXISTS `accounting_app` DEFAULT CHARACTER SET utf8mb4 COLLATE utf8mb4_unicode_ci;
-
-USE `accounting_app`;
 
 -- Users table
 CREATE TABLE IF NOT EXISTS `users` (