feat!: 账号池改渠道网关,对外协议换成 vivid /v1

- 新增 channels/channel_models:上游 URL + AES-GCM 加密 key +
  并发/权重/本地统计,模型经渠道 /v1/models 导入绑定
- internal/upstream:vivid 协议客户端(NDJSON 流 + jobId 断流重连 +
  uploads 预签名 + models + balance + 错误分类)
- service/v1 重写:权重分组调度、Redis 并发槽 conc:c:、故障转移,
  站内/测试/对外统一走渠道执行器
- 对外端点换成 vivid 四件套:POST /v1/generate(NDJSON+jobId 重连)、
  POST /v1/uploads(SigV4 预签名 PUT)、GET /v1/models、GET /v1/balance,
  错误包 {"error":{"code","message"}}
- API key 新发改 vk_+48hex;删除全部内置 provider 与 token 池
- 管理端:渠道 CRUD/拉模型/导入/余额端点,前端账号页换渠道页,
  概览/文档/测试弹窗适配

Generated with [Devin](https://devin.ai)

Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

backend/internal/service/user_generation.go

@@ -40,8 +40,8 @@ type UserGenerateRequest struct {
 	// DeAI applies 去AI特征 post-processing to the generated image (image only)
 	// and charges the per-tier surcharge on top of the model price.
 	DeAI bool
-	// AccountID pins an admin test to one specific provider account (账号生图测试).
-	AccountID string
+	// ChannelID pins an admin test to one specific channel (渠道生图测试).
+	ChannelID string
 }
 
 func (s *UserGenerationService) Generate(ctx context.Context, user *model.User, in UserGenerateRequest) (map[string]any, error) {
@@ -138,7 +138,7 @@ func (s *UserGenerationService) AdminTest(ctx context.Context, user *model.User,
 			AspectRatio:     in.Ratio,
 			Resolution:      in.Resolution,
 			ReferenceImages: in.ReferenceImages,
-			AccountID:       in.AccountID,
+			ChannelID:       in.ChannelID,
 		})
 	default:
 		return s.v1.prepareAdminTestImage(ctx, principal, V1ImageRequest{
@@ -147,7 +147,7 @@ func (s *UserGenerationService) AdminTest(ctx context.Context, user *model.User,
 			AspectRatio:     in.Ratio,
 			Resolution:      in.Resolution,
 			ReferenceImages: in.ReferenceImages,
-			AccountID:       in.AccountID,
+			ChannelID:       in.ChannelID,
 		})
 	}
 }