渠道: 分协议 Base URL + 模型抽屉/远程拉取/操作图标

- 渠道支持分协议 base_url(chat/responses/messages 各一), 网关按协议选 base 直通
  (如智谱三种格式不同 base, 一个渠道即可), UpstreamURL 按 proto 拼接
- 渠道模型改为下方抽屉: 当前绑定列表(内联改上游/解除)、从接口拉取(remote 预览+勾选添加)、手动添加
- 新增 /channels/:id/models/remote 预览接口; 操作按钮加 Phosphor 图标
- 修复 formats jsonb 更新未序列化问题; 手机端渠道卡片化

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

server/internal/channel/health.go

@@ -4,7 +4,6 @@ import (
 	"context"
 	"log"
 	"net/http"
-	"strings"
 	"sync"
 	"time"
 
@@ -83,7 +82,7 @@ func (h *HealthMonitor) probe(ch *store.Channel) {
 		h.record(ch, false)
 		return
 	}
-	url := strings.TrimRight(ch.BaseURL, "/") + "/v1/models"
+	url := ch.UpstreamURL("", "/models")
 	req, _ := http.NewRequest(http.MethodGet, url, nil)
 	req.Header.Set("Authorization", "Bearer "+key)
 	req.Header.Set("Accept", "application/json")