GitLab

- Fix 7 stale comments still mentioning "限制检查" in handlers/services
- Make billingModelForRestriction explicitly list channel_mapped case
- Add slog.Warn for error swallowing in ResolveChannelMapping and
  needsUpstreamChannelRestrictionCheck
- Document sticky session upstream check exemption

Move the model pricing restriction check from 8 handler entry points
to the account scheduling phase (SelectAccountForModelWithExclusions /
SelectAccountWithLoadAwareness), aligning restriction with billing:

- requested: check original request model against pricing list
- channel_mapped: check channel-mapped model against pricing list
- upstream: per-account check using account-mapped model

Handler layer now only resolves channel mapping (no restriction).
Scheduling layer performs pre-check for requested/channel_mapped,
and per-account filtering for upstream billing source.

- 渠道模型映射：支持精确匹配和通配符映射，按平台隔离
- 渠道模型定价：支持 token/按次/图片三种计费模式，区间分层定价
- 模型限制：渠道可限制仅允许定价列表中的模型
- 计费模型来源：支持 requested/upstream 两种计费模型选择
- 用量统计：usage_logs 新增 channel_id/model_mapping_chain/billing_tier/billing_mode 字段
- Dashboard 支持 model_source 维度（requested/upstream/mapping）查看模型统计
- 全部 gateway handler 统一接入 ResolveChannelMappingAndRestrict
- 修复测试：同步 SoraGenerationRepository 接口、SQL INSERT 参数、scan 字段

- 4个缺失handler入口添加渠道映射+限制检查(ChatCompletions/Responses/Gemini)
- 模型限制错误信息优化，区分"模型不可用"和"无账号"
- OpenAI RecordUsage RequestedModel 改用 OriginalModel
- ResolveChannelMappingAndRestrict/ReplaceModelInBody 抽取到 ChannelService 消除跨service重复
- validateNoDuplicateModels 按 platform:model 去重
- 删除 Channel.ResolveMappedModel 死代码和 CalculateCostWithChannel Deprecated方法
- 移除冗余nil检查，抽取 validatePricingBillingMode 公共校验

New HTTP handlers for Anthropic platform groups accepting OpenAI-format
endpoints:

- GatewayHandler.Responses: /v1/responses for non-OpenAI groups
- GatewayHandler.ChatCompletions: /v1/chat/completions for non-OpenAI groups

Both handlers include:
- Claude Code only restriction (403 reject when claude_code_only enabled,
  since these endpoints are never Claude Code clients)
- Full auth → billing → user/account concurrency → failover loop
- Ops error/endpoint context propagation
- Async usage recording via worker pool

Error responses use each endpoint's native format (Responses API format
for /v1/responses, CC format for /v1/chat/completions).