文档: 新增 Docusaurus 官网与双语文档，README 切换为英文默认 (#39)

- 新建 docs-site/ Docusaurus 项目，支持 en + zh-Hans 双语
- 从 README 迁移内容为独立文档页面：
  - Getting Started（安装、快速开始）
  - Deployment（Docker、裸机、Nginx、配置参考）
  - Features（备份类型、存储后端、SAP HANA、多节点集群、通知）
  - Reference（API、CLI）
  - Development（开发、贡献）
- 自定义 BackupX 主题色、logo、落地页组件
- 新增 .github/workflows/docs.yml，Actions 自动构建并发布到 GitHub Pages
- README.md 切换为英文，中文版挪到 README.zh-CN.md，两者均精简为导航型
- 配置站点 URL：https://awuqing.github.io/BackupX/

docs-site/docs/features/notifications.md

@@ -0,0 +1,49 @@
+---
+sidebar_position: 5
+title: Notifications
+description: Email, webhook, and Telegram notifications on backup success or failure.
+---
+
+# Notifications
+
+BackupX supports three notification channels. Configure per-channel rules for success-only, failure-only, or both.
+
+## Email (SMTP)
+
+| Field | Notes |
+|-------|-------|
+| SMTP host / port | e.g. `smtp.gmail.com:587` |
+| Username / password | App-specific password recommended |
+| From address | Used in `From:` header |
+| Recipients | Comma-separated list |
+| Use TLS / StartTLS | Match your SMTP provider |
+
+## Webhook
+
+Send a JSON POST to an arbitrary URL. Body shape:
+
+```json
+{
+  "event": "backup_result",
+  "task": {"id": 1, "name": "web-files", "type": "file"},
+  "record": {"id": 42, "status": "success", "fileSize": 1048576, "durationSeconds": 12},
+  "error": ""
+}
+```
+
+Useful for custom workflows: Slack incoming webhook, PagerDuty, your own API, etc.
+
+## Telegram
+
+| Field | Notes |
+|-------|-------|
+| Bot token | From [@BotFather](https://t.me/BotFather) |
+| Chat ID | Numeric — obtain via `/start` + bot's `getUpdates` |
+
+## Event rules
+
+Each notification configuration can be scoped to:
+
+- **Success only** — quiet during normal runs, pings on first failure
+- **Failure only** — recommended for loud channels
+- **Both** — useful during initial setup to verify notifications flow