Register a DoubaoVideo asset adapter that forwards the Ark-compatible
asset API (POST /api/v1/volcengine/asset?Action=xx) to the official
/openApi/portrait endpoint with a Volcengine V4 HMAC-SHA256 signature
(canonical request over content-type/host/x-content-sha256/x-date,
date/cn-beijing/ark/request scope). The AK/SK pair and optional
project code are stored in channel_asset_credentials (pool_id holds
the project code), so asset credentials stay separate from the video
Bearer key; the channel form now accepts them for type 54.

DoubaoVideo joins the seedance asset family so a user's asset upload
channel and video task channel stay the same (asset:// references
pass through to the upstream). Both resolution chains (asset proxy
resolver and video asset family matcher) now require the asset
credential to be configured before a type-54 channel can serve,
bind, or be auto-matched for assets, falling through to compatible
channels otherwise. The /api/v3 native-path whitelist simplifies
back to the family list now that 54 is a member.

Verified end-to-end against the real upstream: CreateAssetGroup,
CreateAsset (real video upload, Processing -> Active moderation),
ListAssets/GetAsset, and a video generation task referencing the
asset via asset://video reference (succeeded, 432900 tokens).

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

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

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

为 Channel 模型新增 public_name 字段，让管理员可以为每个渠道
设置用户可见的友好名称（如"标准通道"、"高速通道"），替代前端
硬编码的"通道一/二/三"。Playground 通道选择器展示对外名称，
"渠道"统一改为"通道"。新建渠道时对外名称必填，编辑时可选。

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

Add a new /api/user/channels endpoint that returns only enabled channels
with non-sensitive fields (id, name, type, remark) for token channel binding.
Update EditTokenModal to use this endpoint and display remark instead of ID
in the channel dropdown.

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