feat: 增加自定义 meta description; (#1246)

* feat: 增加自定义 meta description;

* fix: 环境变量使用错误;

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Co-authored-by: junshun.mq <junshun.mq@alibaba-inc.com>

packages/global/common/system/types/index.d.ts

@@ -37,6 +37,7 @@ export type FastGPTFeConfigsType = {
   chatbotUrl?: string;
   openAPIDocUrl?: string;
   systemTitle?: string;
+  systemDescription?: string;
   googleClientVerKey?: string;
   isPlus?: boolean;
   show_phoneLogin?: boolean;