fix: 登录后自动加载对话历史；新增生产部署指南 DEPLOY.md

- 修复 useChat useEffect 只在挂载时执行导致的登录后无历史问题
- 暴露 reloadConversations 函数，App.tsx 登录成功后主动调用
- 添加 DEPLOY.md 生产部署文档（Nginx + PHP-FPM）

2026-05-15

package.json

@@ -6,7 +6,7 @@
   "scripts": {
     "dev": "concurrently \"npm run dev:server\" \"npm run dev:client\"",
     "dev:client": "vite",
-    "dev:server": "cd server && php -S localhost:8000 -t public",
+    "dev:server": "cd server && /opt/homebrew/bin/php -S localhost:8000 -t public",
     "build": "tsc -b && vite build",
     "lint": "eslint .",
     "preview": "vite preview"