Co-Authored-By: Codex <noreply@anthropic.com>

Co-Authored-By: Codex <noreply@anthropic.com>

Co-Authored-By: Codex <noreply@anthropic.com>

- 删除 tautological 的 `if channel == nil` 外层判断（channel 在该位置永远为 nil）
- 修正删除指定渠道分支后遗留的多余缩进（减少一级 tab）
- 更新通道亲和性检查注释为简洁版

删除了用户通过 sk-{key}:{channelId} 指定渠道、Playground 下拉框选择渠道、
以及管理员设置默认渠道 (is_default) 的所有后端代码。

涉及修改：
- middleware/auth.go: 简化 parseTokenKey，移除 specific_channel_id 设置
- middleware/distributor.go: 移除指定渠道分发逻辑、默认通道检查、ModelRequest.ChannelId
- constant/context_key.go: 移除 ContextKeyTokenSpecificChannelId
- controller/playground_channels.go: 整个文件删除
- controller/relay.go: 移除 shouldRetry/shouldRetryTaskRelay 中的指定渠道跳过
- controller/channel.go: 移除 GetUserChannelsForBinding
- controller/channel_pricing.go: 移除 SetDefaultChannel/ClearDefaultChannel
- model/ability.go: 移除 GetModelChannelsForGroup
- model/channel.go: 移除 GetAllChannelsForBinding
- model/channel_pricing.go: 移除默认通道缓存及所有相关函数
- model/pricing.go: 移除 DefaultChannelName 字段
- router/api-router.go: 移除 4 条路由
- i18n: 移除 channel.id_format_error 和 distributor.invalid_channel_id

- 错误日志新增 upstream_request_id（从 Anthropic/OpenAI 响应 header 提取）和 upstream_body（截断 2KB）
- 修复 RelayErrorHandler 内部 WithOpenAIError/NewOpenAIError 分支丢失上游字段的 bug
- Playground 渠道和分组改为通过 X-Channel-Id/X-Group header 传递，而非 body 字段
- Distributor 中间件支持从 header 回退读取 channel_id 和 group

Co-Authored-By: Claude <noreply@anthropic.com>

- 新增 /api/user/model_channels 接口，返回模型可用渠道及默认渠道
- Playground 设置面板添加渠道选择下拉框
- Distribute 中间件支持从请求体读取 channel_id 指定渠道
- 支持 URL 参数 ?model=xxx 直接选择模型

Co-Authored-By: Claude <noreply@anthropic.com>

- 新增 is_default 字段和缓存层，支持管理员为模型指定默认通道
- Distribute 中间件优先级调整：Token 指定 → 默认通道 → 亲和性 → 随机
- 模型定价卡片和详情弹窗展示默认通道 amber 标识
- 管理后台定价页面新增星标切换默认通道
- 新增 set_default / clear_default API 和 6 个单元测试
- 简化卡片价格显示（移除内联缓存价格，改为详情弹窗展示）

Co-Authored-By: Claude <noreply@anthropic.com>

- Add support for sk-{key}:{channelId} format to specify channel dynamically
- Remove BoundChannelId field and related code
- All users can now specify channels, not just admins
- Add model validation when channel is specified
- Remove bound channel UI from token management

Breaking change: tokens can no longer be bound to channels at creation time.
Use sk-{key}:{channelId} format instead.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

When a token has BoundChannelId set, the distributor now uses that channel
instead of the normal channel selection process. The bound channel is still
validated to ensure it is enabled and supports the requested model.

Changes:
- Add ContextKeyTokenBoundChannelId constant
- Set bound channel in context during token authentication
- Check and use bound channel in distributor before normal selection

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>