GitLab

- Extract postUsageBilling() to consolidate billing logic across
  GatewayService.RecordUsage, RecordUsageWithLongContext, and
  OpenAIGatewayService.RecordUsage, eliminating ~120 lines of
  duplicated code
- Fix account quota to use TotalCost × accountRateMultiplier
  (was using raw TotalCost, inconsistent with account cost stats)
- Fix RecordUsageWithLongContext API Key quota only updating in
  balance mode (now updates regardless of billing type)
- Fix WebSocket client disconnect detection on Windows by adding
  "an established connection was aborted" to known disconnect errors

新增 OpenAI WebSocket v2 passthrough relay 数据面与服务适配层，
支持按账号 ws mode 在 ctx_pool 与 passthrough 间路由。

同步调整前端 OpenAI ws mode 选项为 off/ctx_pool/passthrough，
并补充 i18n 文案与对应单测。

新增 Caddyfile.dmit 与 docker-compose-aicodex.yml 部署配置，
用于宿主机场景下的反向代理与服务编排。
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>