fix(openai): trigger account failover on passthrough 403 forbidden_error

[Nimm0ny]

问题

OpenAI passthrough 模式(走 OAuth 桥接的 Codex / ChatGPT 订阅账号)的失败转移决策函数 shouldFailoverOpenAIPassthroughResponse 当前只把 429 和 529 当作可 failover 状态码:

// backend/internal/service/openai_gateway_service.go:3086
func shouldFailoverOpenAIPassthroughResponse(statusCode int) bool {
    switch statusCode {
    case http.StatusTooManyRequests, 529:
        return true
    default:
        return false
    }
}

但 Codex / ChatGPT 订阅账号的"用量配额耗尽"信号实际是 403 forbidden_error (例如 {"error": {"message": "usage limit reached", "type": "forbidden_error"}}),不是 429。这意味着:

• 客户 API key 在 group 内绑定多个 OAuth 账号
• 当前账号配额跑完返回 403
• vanilla 不 failover,把 403 原样透回客户端
• 用户体验:单账号跑完后 key 直接断开,即使同 group 还有健康账号

跟 shouldFailoverUpstreamError(用于非 passthrough 的标准模式)对比,后者已经包含 case 401, 402, 403, 429, 529 — passthrough 路径漏掉了 403。

改动

shouldFailoverOpenAIPassthroughResponse 增加 http.StatusForbidden,让 passthrough 模式也能在 403 时触发 handler.FailoverState 循环。

复用现有的 cooldown 状态机(SetTempUnschedulable + IncrementOpenAI403Count),不引入新状态:

• 单次 403:账号进入 10 分钟临时冷却("OpenAI 403 temporary cooldown"),group 内调度器立即跳过它
• 累计 3 次 403:升级为永久判坏号(走 SetError 路径)

测试

TestOpenAIGatewayService_OpenAIPassthrough_FailoverStatusesTriggerAccountSwitch 增加 oauth_403_temp_unschedulable case,验证:

• repo.tempUnschedulableIDs == [123]
• until 在 9 分钟之后(=10 分钟 cooldown)
• repo.tempUnschedulableWhy[0] 包含 "OpenAI 403 temporary cooldown"

本地 go test ./internal/service -run TestOpenAIGatewayService_OpenAIPassthrough_FailoverStatusesTriggerAccountSwitch -count=1 -v 全部通过(5 个 subcase)。

兼容性

• 非 passthrough 路径不受影响(那条路 vanilla 已经处理 403)
• 单次 403 不会立刻判坏账号 — 临时冷却 10 分钟,符合 sub2api 现有的"先临时冷却,再根据连续次数决定是否判坏号"逻辑(commit 11cf23da 提过同样思路)

[github-actions]

Thank you for your contribution! Before we can merge this PR, we need you to sign our Contributor License Agreement (CLA).

To sign, please reply with the following comment:

I have read the CLA Document and I hereby sign the CLA

You only need to sign once — it will be valid for all your future contributions to this project.

---

I have read the CLA Document and I hereby sign the CLA

---

_{You can retrigger this bot by commenting recheck in this Pull Request. Posted by the CLA Assistant Lite bot.}