fix: 启动时自动迁移缺失的数据库列

问题：旧版数据库缺少 user_id 列导致 500 错误
修复：
- init.ts 启动时自动检测并添加缺失列
- 删除 deploy/ 目录，改为手动部署
- 添加 migrate.sql 迁移脚本
- 更新 CLAUDE.md 部署说明

server/src/db/init.ts

@@ -3,6 +3,31 @@ import pool from './connection'
 import { readFileSync } from 'fs'
 import { join } from 'path'
 
+async function columnExists(conn: mysql.Connection, table: string, column: string): Promise<boolean> {
+  const [rows] = await conn.query(
+    `SELECT COUNT(*) as cnt FROM information_schema.COLUMNS WHERE TABLE_SCHEMA = DATABASE() AND TABLE_NAME = ? AND COLUMN_NAME = ?`,
+    [table, column]
+  )
+  return (rows as any[])[0].cnt > 0
+}
+
+async function runMigrations(conn: mysql.Connection) {
+  // transactions 表添加 user_id
+  if (!await columnExists(conn, 'transactions', 'user_id')) {
+    console.log('[DB] Migrating: adding user_id to transactions')
+    await conn.query('ALTER TABLE transactions ADD COLUMN user_id INT NOT NULL DEFAULT 1 AFTER id')
+    await conn.query('ALTER TABLE transactions ADD INDEX idx_user_date (user_id, date)')
+    await conn.query('ALTER TABLE transactions ADD INDEX idx_user_type_date (user_id, type, date)')
+  }
+
+  // budgets 表添加 user_id
+  if (!await columnExists(conn, 'budgets', 'user_id')) {
+    console.log('[DB] Migrating: adding user_id to budgets')
+    await conn.query('ALTER TABLE budgets ADD COLUMN user_id INT NOT NULL DEFAULT 1 AFTER id')
+    await conn.query('ALTER TABLE budgets ADD UNIQUE KEY uk_user_month (user_id, month)')
+  }
+}
+
 export async function initDatabase() {
   const dbName = process.env.DB_NAME || 'xiaocai'
 
@@ -38,10 +63,14 @@ export async function initDatabase() {
     const seed = readFileSync(seedPath, 'utf-8')
     await initConn.query(seed)
 
+    // 运行迁移（添加缺失列）
+    await runMigrations(initConn)
+
     console.log('[DB] Database initialized')
   } catch (err: any) {
     if (err.code === 'ER_DUP_ENTRY' || err.errno === 1062) {
       console.log('[DB] Already initialized, skipping seed')
+      await runMigrations(initConn)
     } else {
       console.error('[DB] Init failed:', err.message)
     }