feat(admin): 重构系统设置页面并新增渠道管理功能

- 将系统设置页面改为公开/私有双标签页结构
- 新增渠道协议、权重配置和加权随机选择算法
- 替换自定义模型为自定义渠道配置选项
- 实现渠道模型远程获取和在线测试功能
- 添加批量测试和抽屉式编辑界面
- 更新文档说明和数据表结构定义

service/settings.go

@@ -1,6 +1,10 @@
 package service
 
 import (
+	"errors"
+	"math/rand"
+	"strings"
+
 	"github.com/basketikun/infinite-canvas/model"
 	"github.com/basketikun/infinite-canvas/repository"
 )
@@ -37,9 +41,54 @@ func normalizePrivateSetting(setting model.PrivateSetting) model.PrivateSetting
 		setting.Channels = []model.ModelChannel{}
 	}
 	for i := range setting.Channels {
+		if setting.Channels[i].Protocol == "" {
+			setting.Channels[i].Protocol = "openai"
+		}
 		if setting.Channels[i].Models == nil {
 			setting.Channels[i].Models = []string{}
 		}
+		if setting.Channels[i].Weight <= 0 {
+			setting.Channels[i].Weight = 1
+		}
 	}
 	return setting
 }
+
+func SelectModelChannel(modelName string) (model.ModelChannel, error) {
+	settings, err := repository.GetSettings()
+	if err != nil {
+		return model.ModelChannel{}, err
+	}
+	channels := modelChannelsForModel(normalizePrivateSetting(settings.Private).Channels, modelName)
+	if len(channels) == 0 {
+		return model.ModelChannel{}, errors.New("没有可用模型渠道")
+	}
+	total := 0
+	for _, channel := range channels {
+		total += channel.Weight
+	}
+	hit := rand.Intn(total)
+	for _, channel := range channels {
+		hit -= channel.Weight
+		if hit < 0 {
+			return channel, nil
+		}
+	}
+	return channels[0], nil
+}
+
+func modelChannelsForModel(channels []model.ModelChannel, modelName string) []model.ModelChannel {
+	result := []model.ModelChannel{}
+	for _, channel := range channels {
+		if !channel.Enabled || channel.BaseURL == "" || channel.APIKey == "" {
+			continue
+		}
+		for _, item := range channel.Models {
+			if strings.TrimSpace(item) == modelName {
+				result = append(result, channel)
+				break
+			}
+		}
+	}
+	return result
+}