渠道: 远程候选按渠道过滤 + key 掩码 + 移除批量导入端点

- 远程模型候选只排除本渠道已允许的模型，同名模型可被多个渠道各自允许
- 渠道 key 掩码统一 xxxxxxx******Mq4Y（保留前 7 位与后 4 位）
- 移除已弃用的批量导入端点 POST /channels/:id/models/import

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

server/internal/api/router.go

@@ -103,7 +103,6 @@ func NewRouter(a *app.App, gw *proxy.Gateway) *gin.Engine {
 			admin.PUT("/channels/:id", h.AdminUpdateChannel)
 			admin.DELETE("/channels/:id", h.AdminDeleteChannel)
 			admin.POST("/channels/:id/test", h.AdminTestChannel)
-			admin.POST("/channels/:id/models/import", h.AdminImportChannelModels)
 			admin.GET("/channels/:id/models/remote", h.AdminChannelRemoteModels)
 			admin.GET("/channels/:id/models", h.AdminChannelModels)
 			admin.POST("/channels/:id/models", h.AdminChannelAddModel)
@@ -111,6 +110,7 @@ func NewRouter(a *app.App, gw *proxy.Gateway) *gin.Engine {
 			admin.DELETE("/channels/:id/models/:bid", h.AdminChannelDeleteModel)
 			// 模型与定价
 			admin.GET("/models", h.AdminModels)
+			admin.DELETE("/models/unused", h.AdminDeleteUnusedModels)
 			admin.POST("/models", h.AdminCreateModel)
 			admin.PUT("/models/:id", h.AdminUpdateModel)
 			admin.DELETE("/models/:id", h.AdminDeleteModel)