merge main 并修复与 #5730 的语义冲突

main 侧 #5730 新增的 openai_gateway_cn_fixes_test.go 按旧 11 参签名调用
calculateOpenAIRecordUsageCost；本分支为该函数新增了第 12 个参数
pricingAt。文本无冲突但 test build 会失败，此处按本分支对同类测试
调用点的既有处理方式补传 time.Time{}。

backend/internal/handler/admin/group_handler.go

@@ -98,7 +98,7 @@ func NewGroupHandler(adminService service.AdminService, dashboardService *servic
 type CreateGroupRequest struct {
 	Name                      string                        `json:"name" binding:"required"`
 	Description               string                        `json:"description"`
-	Platform                  string                        `json:"platform" binding:"omitempty,oneof=anthropic openai gemini antigravity grok composite"`
+	Platform                  string                        `json:"platform" binding:"omitempty,oneof=anthropic openai gemini antigravity grok kimi zhipu deepseek composite"`
 	RateMultiplier            float64                       `json:"rate_multiplier"`
 	IsExclusive               bool                          `json:"is_exclusive"`
 	SubscriptionType          string                        `json:"subscription_type" binding:"omitempty,oneof=standard subscription"`
@@ -166,7 +166,7 @@ type CreateGroupRequest struct {
 type UpdateGroupRequest struct {
 	Name                      string                         `json:"name"`
 	Description               *string                        `json:"description"`
-	Platform                  string                         `json:"platform" binding:"omitempty,oneof=anthropic openai gemini antigravity grok composite"`
+	Platform                  string                         `json:"platform" binding:"omitempty,oneof=anthropic openai gemini antigravity grok kimi zhipu deepseek composite"`
 	RateMultiplier            *float64                       `json:"rate_multiplier"`
 	IsExclusive               *bool                          `json:"is_exclusive"`
 	Status                    string                         `json:"status" binding:"omitempty,oneof=active inactive"`

backend/internal/handler/admin/group_handler_platform_test.go

@@ -0,0 +1,83 @@
+//go:build unit
+
+package admin
+
+import (
+	"bytes"
+	"fmt"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/gin-gonic/gin"
+	"github.com/stretchr/testify/require"
+)
+
+// 回归分组平台枚举:kimi/zhipu/deepseek 必须能通过 Create/Update 的 binding 校验
+// （历史 bug:调度/路由链路已支持 CN 平台分组,但 oneof 白名单漏加三平台,导致
+// 平台分组无法创建、CN 账号"无可用分组"）;非法值仍须被拒。
+func bindGroupPlatformJSON(t *testing.T, target any, body string) error {
+	t.Helper()
+	gin.SetMode(gin.TestMode)
+	c, _ := gin.CreateTestContext(httptest.NewRecorder())
+	c.Request = httptest.NewRequest("POST", "/", bytes.NewBufferString(body))
+	c.Request.Header.Set("Content-Type", "application/json")
+	return c.ShouldBindJSON(target)
+}
+
+func TestGroupPlatformBinding_AllowedPlatforms(t *testing.T) {
+	allowed := []string{
+		"anthropic", "openai", "gemini", "antigravity", "grok",
+		"kimi", "zhipu", "deepseek", "composite",
+	}
+	for _, platform := range allowed {
+		t.Run("create_"+platform, func(t *testing.T) {
+			var req CreateGroupRequest
+			body := fmt.Sprintf(`{"name":"g","platform":%q}`, platform)
+			require.NoError(t, bindGroupPlatformJSON(t, &req, body),
+				"platform %q 应通过 CreateGroupRequest 校验", platform)
+			require.Equal(t, platform, req.Platform)
+		})
+		t.Run("update_"+platform, func(t *testing.T) {
+			var req UpdateGroupRequest
+			body := fmt.Sprintf(`{"platform":%q}`, platform)
+			require.NoError(t, bindGroupPlatformJSON(t, &req, body),
+				"platform %q 应通过 UpdateGroupRequest 校验", platform)
+			require.Equal(t, platform, req.Platform)
+		})
+	}
+}
+
+func TestGroupPlatformBinding_RejectsInvalidPlatforms(t *testing.T) {
+	invalid := []string{
+		"moonshot", // 厂商别名,不是平台标识
+		"Kimi",     // 大小写敏感
+		"openai ",  // 尾随空格
+		"glm",
+		"bogus",
+	}
+	for _, platform := range invalid {
+		t.Run("create_"+platform, func(t *testing.T) {
+			var req CreateGroupRequest
+			body := fmt.Sprintf(`{"name":"g","platform":%q}`, platform)
+			require.Error(t, bindGroupPlatformJSON(t, &req, body),
+				"platform %q 应被 CreateGroupRequest 拒绝", platform)
+		})
+		t.Run("update_"+platform, func(t *testing.T) {
+			var req UpdateGroupRequest
+			body := fmt.Sprintf(`{"platform":%q}`, platform)
+			require.Error(t, bindGroupPlatformJSON(t, &req, body),
+				"platform %q 应被 UpdateGroupRequest 拒绝", platform)
+		})
+	}
+}
+
+// 守住 composite 路由目标不放行 CN:CN 平台不可作为 composite 路由目标
+// （DetectModelPlatform/isConcreteRequestPlatform 均无 CN 分支,放行即打开半实现路径）。
+func TestCompositeRouteTargetPlatform_StillExcludesCNProviders(t *testing.T) {
+	for _, platform := range []string{"kimi", "zhipu", "deepseek"} {
+		var req CompositeRouteRequest
+		body := fmt.Sprintf(`{"public_model":"m","target_platform":%q}`, platform)
+		require.Error(t, bindGroupPlatformJSON(t, &req, body),
+			"composite target_platform %q 应保持被拒", platform)
+	}
+}