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/index.js

@@ -0,0 +1,24 @@
+const ClaudeBalanceProvider = require('./claudeBalanceProvider')
+const ClaudeConsoleBalanceProvider = require('./claudeConsoleBalanceProvider')
+const OpenAIResponsesBalanceProvider = require('./openaiResponsesBalanceProvider')
+const GenericBalanceProvider = require('./genericBalanceProvider')
+
+function registerAllProviders(balanceService) {
+  // Claude
+  balanceService.registerProvider('claude', new ClaudeBalanceProvider())
+  balanceService.registerProvider('claude-console', new ClaudeConsoleBalanceProvider())
+
+  // OpenAI / Codex
+  balanceService.registerProvider('openai-responses', new OpenAIResponsesBalanceProvider())
+  balanceService.registerProvider('openai', new GenericBalanceProvider('openai'))
+  balanceService.registerProvider('azure_openai', new GenericBalanceProvider('azure_openai'))
+
+  // 其他平台（降级）
+  balanceService.registerProvider('gemini', new GenericBalanceProvider('gemini'))
+  balanceService.registerProvider('gemini-api', new GenericBalanceProvider('gemini-api'))
+  balanceService.registerProvider('bedrock', new GenericBalanceProvider('bedrock'))
+  balanceService.registerProvider('droid', new GenericBalanceProvider('droid'))
+  balanceService.registerProvider('ccr', new GenericBalanceProvider('ccr'))
+}
+
+module.exports = { registerAllProviders }