feat(admin): 新增账户余额/配额查询与展示

- 新增 accountBalanceService 与多 Provider 适配（Claude/Claude Console/OpenAI Responses/通用）
  - Redis 增加余额查询结果与本地统计缓存读写
  - 管理端新增 /admin/accounts/balance 相关接口与汇总接口，并在应用启动时注册 Provider
  - 后台前端新增余额组件与 Dashboard 余额/配额汇总、低余额/高使用提示
  - 补充 accountBalanceService 单元测试

src/services/balanceProviders/baseBalanceProvider.js

@@ -0,0 +1,133 @@
+const axios = require('axios')
+const logger = require('../../utils/logger')
+const ProxyHelper = require('../../utils/proxyHelper')
+
+/**
+ * Provider 抽象基类
+ * 各平台 Provider 需继承并实现 queryBalance(account)
+ */
+class BaseBalanceProvider {
+  constructor(platform) {
+    this.platform = platform
+    this.logger = logger
+  }
+
+  /**
+   * 查询余额（抽象方法）
+   * @param {object} account - 账户对象
+   * @returns {Promise<object>}
+   * 形如：
+   * {
+   *   balance: number|null,
+   *   currency?: string,
+   *   quota?: { daily, used, remaining, resetAt, percentage, unlimited? },
+   *   queryMethod?: 'api'|'field'|'local',
+   *   rawData?: any
+   * }
+   */
+  async queryBalance(_account) {
+    throw new Error('queryBalance 方法必须由子类实现')
+  }
+
+  /**
+   * 通用 HTTP 请求方法（支持代理）
+   * @param {string} url
+   * @param {object} options
+   * @param {object} account
+   */
+  async makeRequest(url, options = {}, account = {}) {
+    const config = {
+      url,
+      method: options.method || 'GET',
+      headers: options.headers || {},
+      timeout: options.timeout || 15000,
+      data: options.data,
+      params: options.params,
+      responseType: options.responseType
+    }
+
+    const proxyConfig = account.proxyConfig || account.proxy
+    if (proxyConfig) {
+      const agent = ProxyHelper.createProxyAgent(proxyConfig)
+      if (agent) {
+        config.httpAgent = agent
+        config.httpsAgent = agent
+        config.proxy = false
+      }
+    }
+
+    try {
+      const response = await axios(config)
+      return {
+        success: true,
+        data: response.data,
+        status: response.status,
+        headers: response.headers
+      }
+    } catch (error) {
+      const status = error.response?.status
+      const message = error.response?.data?.message || error.message || '请求失败'
+      this.logger.debug(`余额 Provider HTTP 请求失败: ${url} (${this.platform})`, {
+        status,
+        message
+      })
+      return { success: false, status, error: message }
+    }
+  }
+
+  /**
+   * 从账户字段读取 dailyQuota / dailyUsage（通用降级方案）
+   * 注意：部分平台 dailyUsage 字段可能不是实时值，最终以 AccountBalanceService 的本地统计为准
+   */
+  readQuotaFromFields(account) {
+    const dailyQuota = Number(account?.dailyQuota || 0)
+    const dailyUsage = Number(account?.dailyUsage || 0)
+
+    // 无限制
+    if (!Number.isFinite(dailyQuota) || dailyQuota <= 0) {
+      return {
+        balance: null,
+        currency: 'USD',
+        quota: {
+          daily: Infinity,
+          used: Number.isFinite(dailyUsage) ? dailyUsage : 0,
+          remaining: Infinity,
+          percentage: 0,
+          unlimited: true
+        },
+        queryMethod: 'field'
+      }
+    }
+
+    const used = Number.isFinite(dailyUsage) ? dailyUsage : 0
+    const remaining = Math.max(0, dailyQuota - used)
+    const percentage = dailyQuota > 0 ? (used / dailyQuota) * 100 : 0
+
+    return {
+      balance: remaining,
+      currency: 'USD',
+      quota: {
+        daily: dailyQuota,
+        used,
+        remaining,
+        percentage: Math.round(percentage * 100) / 100
+      },
+      queryMethod: 'field'
+    }
+  }
+
+  parseCurrency(data) {
+    return data?.currency || data?.Currency || 'USD'
+  }
+
+  async safeExecute(fn, fallbackValue = null) {
+    try {
+      return await fn()
+    } catch (error) {
+      this.logger.error(`余额 Provider 执行失败: ${this.platform}`, error)
+      return fallbackValue
+    }
+  }
+}
+
+module.exports = BaseBalanceProvider