feat: 添加账号异常状态 Webhook 通知功能

## 功能概述
- 新增账号禁用/异常状态的 Webhook 实时通知机制
- 支持 Claude OAuth、Claude Console、Gemini 三种平台的账号监控
- 提供完整的 Webhook 管理 API 和配置选项

## 主要变更

### 新增文件
- `src/utils/webhookNotifier.js`: Webhook 通知核心服务
- `src/routes/webhook.js`: Webhook 管理 API 路由

### 功能集成
- Claude OAuth 账号：unauthorized 状态 + token 刷新错误通知
- Claude Console 账号：blocked 状态通知
- Gemini 账号：token 刷新错误通知

### 配置支持
- 新增环境变量：WEBHOOK_ENABLED, WEBHOOK_URLS, WEBHOOK_TIMEOUT, WEBHOOK_RETRIES
- 支持多个 Webhook URL 并发通知
- 自动重试机制（指数退避）+ 超时保护

### 管理端点
- POST /admin/webhook/test: 测试连通性
- POST /admin/webhook/test-notification: 发送测试通知
- GET /admin/webhook/config: 查看配置信息

## 通知格式
```json
{
  "type": "account_anomaly",
  "data": {
    "accountId": "uuid",
    "accountName": "账号名称",
    "platform": "claude-oauth|claude-console|gemini",
    "status": "unauthorized|blocked|error",
    "errorCode": "CLAUDE_OAUTH_UNAUTHORIZED",
    "reason": "具体异常原因",
    "timestamp": "2025-01-13T10:30:00.000Z"
  }
}
```

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

src/utils/webhookNotifier.js

@@ -0,0 +1,144 @@
+const axios = require('axios')
+const logger = require('./logger')
+const config = require('../../config/config')
+
+class WebhookNotifier {
+  constructor() {
+    this.webhookUrls = config.webhook?.urls || []
+    this.timeout = config.webhook?.timeout || 10000
+    this.retries = config.webhook?.retries || 3
+    this.enabled = config.webhook?.enabled !== false
+  }
+
+  /**
+   * 发送账号异常通知
+   * @param {Object} notification - 通知内容
+   * @param {string} notification.accountId - 账号ID
+   * @param {string} notification.accountName - 账号名称
+   * @param {string} notification.platform - 平台类型 (claude-oauth, claude-console, gemini)
+   * @param {string} notification.status - 异常状态 (unauthorized, blocked, error)
+   * @param {string} notification.errorCode - 异常代码
+   * @param {string} notification.reason - 异常原因
+   * @param {string} notification.timestamp - 时间戳
+   */
+  async sendAccountAnomalyNotification(notification) {
+    if (!this.enabled || this.webhookUrls.length === 0) {
+      logger.debug('Webhook notification disabled or no URLs configured')
+      return
+    }
+
+    const payload = {
+      type: 'account_anomaly',
+      data: {
+        accountId: notification.accountId,
+        accountName: notification.accountName,
+        platform: notification.platform,
+        status: notification.status,
+        errorCode: notification.errorCode,
+        reason: notification.reason,
+        timestamp: notification.timestamp || new Date().toISOString(),
+        service: 'claude-relay-service'
+      }
+    }
+
+    logger.info(
+      `📢 Sending account anomaly webhook notification: ${notification.accountName} (${notification.accountId}) - ${notification.status}`
+    )
+
+    const promises = this.webhookUrls.map((url) => this._sendWebhook(url, payload))
+
+    try {
+      await Promise.allSettled(promises)
+    } catch (error) {
+      logger.error('Failed to send webhook notifications:', error)
+    }
+  }
+
+  /**
+   * 发送Webhook请求
+   * @param {string} url - Webhook URL
+   * @param {Object} payload - 请求载荷
+   */
+  async _sendWebhook(url, payload, attempt = 1) {
+    try {
+      const response = await axios.post(url, payload, {
+        timeout: this.timeout,
+        headers: {
+          'Content-Type': 'application/json',
+          'User-Agent': 'claude-relay-service/webhook-notifier'
+        }
+      })
+
+      if (response.status >= 200 && response.status < 300) {
+        logger.info(`✅ Webhook sent successfully to ${url}`)
+      } else {
+        throw new Error(`HTTP ${response.status}: ${response.statusText}`)
+      }
+    } catch (error) {
+      logger.error(
+        `❌ Failed to send webhook to ${url} (attempt ${attempt}/${this.retries}):`,
+        error.message
+      )
+
+      // 重试机制
+      if (attempt < this.retries) {
+        const delay = Math.pow(2, attempt - 1) * 1000 // 指数退避
+        logger.info(`🔄 Retrying webhook to ${url} in ${delay}ms...`)
+
+        await new Promise((resolve) => setTimeout(resolve, delay))
+        return this._sendWebhook(url, payload, attempt + 1)
+      }
+
+      logger.error(`💥 All ${this.retries} webhook attempts failed for ${url}`)
+    }
+  }
+
+  /**
+   * 测试Webhook连通性
+   * @param {string} url - Webhook URL
+   */
+  async testWebhook(url) {
+    const testPayload = {
+      type: 'test',
+      data: {
+        message: 'Claude Relay Service webhook test',
+        timestamp: new Date().toISOString(),
+        service: 'claude-relay-service'
+      }
+    }
+
+    try {
+      await this._sendWebhook(url, testPayload)
+      return { success: true }
+    } catch (error) {
+      return { success: false, error: error.message }
+    }
+  }
+
+  /**
+   * 获取错误代码映射
+   * @param {string} platform - 平台类型
+   * @param {string} status - 状态
+   * @param {string} reason - 原因
+   */
+  _getErrorCode(platform, status, reason) {
+    const errorCodes = {
+      'claude-oauth': {
+        unauthorized: 'CLAUDE_OAUTH_UNAUTHORIZED',
+        error: 'CLAUDE_OAUTH_ERROR'
+      },
+      'claude-console': {
+        blocked: 'CLAUDE_CONSOLE_BLOCKED',
+        error: 'CLAUDE_CONSOLE_ERROR'
+      },
+      gemini: {
+        error: 'GEMINI_ERROR',
+        unauthorized: 'GEMINI_UNAUTHORIZED'
+      }
+    }
+
+    return errorCodes[platform]?.[status] || 'UNKNOWN_ERROR'
+  }
+}
+
+module.exports = new WebhookNotifier()