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/http/handler/channel_admin.go

@@ -0,0 +1,122 @@
+package handler
+
+import (
+	"errors"
+	"net/http"
+	"strings"
+
+	"backend/internal/service"
+	"backend/internal/upstream"
+
+	"github.com/gin-gonic/gin"
+	"gorm.io/gorm"
+)
+
+// ChannelAdminHandler exposes channel CRUD + upstream model import under
+// /admin/api/channels*. Replaces the old token/account admin surface.
+type ChannelAdminHandler struct {
+	channels *service.ChannelService
+}
+
+func NewChannelAdminHandler(channels *service.ChannelService) *ChannelAdminHandler {
+	return &ChannelAdminHandler{channels: channels}
+}
+
+func (h *ChannelAdminHandler) List(c *gin.Context) {
+	data, err := h.channels.List(c.Request.Context())
+	if err != nil {
+		c.JSON(http.StatusInternalServerError, gin.H{"detail": "failed to load channels"})
+		return
+	}
+	c.JSON(http.StatusOK, gin.H{"data": data})
+}
+
+func (h *ChannelAdminHandler) Save(c *gin.Context) {
+	var body service.SaveChannelDto
+	if err := c.ShouldBindJSON(&body); err != nil {
+		c.JSON(http.StatusBadRequest, gin.H{"detail": "invalid request body"})
+		return
+	}
+	body.BaseURL = strings.TrimSpace(body.BaseURL)
+	ch, err := h.channels.Save(c.Request.Context(), body)
+	if err != nil {
+		if errors.Is(err, gorm.ErrRecordNotFound) {
+			c.JSON(http.StatusNotFound, gin.H{"detail": "channel not found"})
+			return
+		}
+		c.JSON(http.StatusBadRequest, gin.H{"detail": err.Error()})
+		return
+	}
+	c.JSON(http.StatusOK, gin.H{"ok": true, "id": ch.ID})
+}
+
+func (h *ChannelAdminHandler) Delete(c *gin.Context) {
+	var body struct {
+		ID string `json:"id"`
+	}
+	if err := c.ShouldBindJSON(&body); err != nil || strings.TrimSpace(body.ID) == "" {
+		c.JSON(http.StatusBadRequest, gin.H{"detail": "channel id required"})
+		return
+	}
+	if err := h.channels.Delete(c.Request.Context(), body.ID); err != nil {
+		if errors.Is(err, gorm.ErrRecordNotFound) {
+			c.JSON(http.StatusNotFound, gin.H{"detail": "channel not found"})
+			return
+		}
+		c.JSON(http.StatusInternalServerError, gin.H{"detail": err.Error()})
+		return
+	}
+	c.JSON(http.StatusOK, gin.H{"ok": true})
+}
+
+// FetchModels proxies GET /v1/models on a channel (stored creds or ad-hoc
+// base_url+api_key for a not-yet-saved channel form).
+func (h *ChannelAdminHandler) FetchModels(c *gin.Context) {
+	var body service.FetchModelsDto
+	if err := c.ShouldBindJSON(&body); err != nil {
+		c.JSON(http.StatusBadRequest, gin.H{"detail": "invalid request body"})
+		return
+	}
+	items, err := h.channels.FetchModels(c.Request.Context(), body)
+	if err != nil {
+		writeUpstreamErr(c, err)
+		return
+	}
+	if items == nil {
+		items = []upstream.RemoteModel{}
+	}
+	c.JSON(http.StatusOK, gin.H{"data": items})
+}
+
+// ImportModels binds the ticked upstream models to the channel (creating local
+// model rows on first import).
+func (h *ChannelAdminHandler) ImportModels(c *gin.Context) {
+	var body struct {
+		ID     string                     `json:"id"`
+		Models []service.ChannelModelSpec `json:"models"`
+	}
+	if err := c.ShouldBindJSON(&body); err != nil || strings.TrimSpace(body.ID) == "" {
+		c.JSON(http.StatusBadRequest, gin.H{"detail": "channel id required"})
+		return
+	}
+	if err := h.channels.ImportModels(c.Request.Context(), body.ID, body.Models); err != nil {
+		writeUpstreamErr(c, err)
+		return
+	}
+	c.JSON(http.StatusOK, gin.H{"ok": true})
+}
+
+// writeUpstreamErr translates upstream-protocol errors into sensible admin
+// responses (auth → 400 with the upstream's message, temporary → 502).
+func writeUpstreamErr(c *gin.Context, err error) {
+	switch {
+	case errors.Is(err, upstream.ErrAuth):
+		c.JSON(http.StatusBadRequest, gin.H{"detail": "上游鉴权失败：" + err.Error()})
+	case errors.Is(err, upstream.ErrInvalid):
+		c.JSON(http.StatusBadRequest, gin.H{"detail": err.Error()})
+	case errors.Is(err, gorm.ErrRecordNotFound):
+		c.JSON(http.StatusNotFound, gin.H{"detail": "channel not found"})
+	default:
+		c.JSON(http.StatusBadGateway, gin.H{"detail": "上游请求失败：" + err.Error()})
+	}
+}