功能：完善渠道模型批量操作

支持模型管理批量删除，并在拉取模型时提供全选、取消全选和选择数量提示。

同时保持首屏品牌中立，补充后端原子删除与管理员界面回归测试。

backend/internal/handler/finance.go

@@ -269,6 +269,27 @@ func RegisterFinanceRoutes(r *gin.RouterGroup, svc *service.Service) {
 	r.POST("/admin/channels/:id/models", func(c *gin.Context) {
 		saveChannelModel(c, svc, "")
 	})
+	r.POST("/admin/channels/:id/models/batch-delete", func(c *gin.Context) {
+		user, err := currentUser(c, svc)
+		if err != nil {
+			failService(c, err)
+			return
+		}
+		c.Request.Body = http.MaxBytesReader(c.Writer, c.Request.Body, 32<<10)
+		var req struct {
+			ModelIDs []string `json:"modelIds"`
+		}
+		if err := c.ShouldBindJSON(&req); err != nil {
+			fail(c, http.StatusBadRequest, err)
+			return
+		}
+		deleted, err := svc.DeleteAdminChannelModels(user, c.Param("id"), req.ModelIDs)
+		if err != nil {
+			failService(c, err)
+			return
+		}
+		ok(c, gin.H{"deleted": deleted})
+	})
 	r.PATCH("/admin/channels/:id/models/:modelId", func(c *gin.Context) {
 		saveChannelModel(c, svc, c.Param("modelId"))
 	})

backend/internal/handler/finance_routes_test.go

@@ -0,0 +1,23 @@
+package handler
+
+import (
+	"testing"
+
+	"infinite-canvas/backend/internal/service"
+
+	"github.com/gin-gonic/gin"
+)
+
+func TestFinanceRoutesExposeChannelModelBatchDelete(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+	router := gin.New()
+	RegisterFinanceRoutes(router.Group("/api"), &service.Service{})
+
+	const wanted = "POST /api/admin/channels/:id/models/batch-delete"
+	for _, route := range router.Routes() {
+		if route.Method+" "+route.Path == wanted {
+			return
+		}
+	}
+	t.Fatalf("route %s is not registered", wanted)
+}