feat(ops): 运维监控新增 OpenAI Token 请求统计表

- 新增管理端接口 /api/v1/admin/ops/dashboard/openai-token-stats，按模型聚合统计 gpt% 请求

- 支持 time_range=30m|1h|1d|15d|30d（默认 30d），支持 platform/group_id 过滤

- 支持分页（page/page_size）或 TopN（top_n）互斥查询

- 前端运维监控页新增统计表卡片，包含空态/错误态与分页/TopN 交互

- 补齐后端与前端测试

backend/internal/service/ops_openai_token_stats_test.go

@@ -0,0 +1,162 @@
+package service
+
+import (
+	"context"
+	"testing"
+	"time"
+
+	infraerrors "github.com/Wei-Shaw/sub2api/internal/pkg/errors"
+	"github.com/stretchr/testify/require"
+)
+
+type openAITokenStatsRepoStub struct {
+	OpsRepository
+	resp     *OpsOpenAITokenStatsResponse
+	err      error
+	captured *OpsOpenAITokenStatsFilter
+}
+
+func (s *openAITokenStatsRepoStub) GetOpenAITokenStats(ctx context.Context, filter *OpsOpenAITokenStatsFilter) (*OpsOpenAITokenStatsResponse, error) {
+	s.captured = filter
+	if s.err != nil {
+		return nil, s.err
+	}
+	if s.resp != nil {
+		return s.resp, nil
+	}
+	return &OpsOpenAITokenStatsResponse{}, nil
+}
+
+func TestOpsServiceGetOpenAITokenStats_Validation(t *testing.T) {
+	now := time.Now().UTC()
+
+	tests := []struct {
+		name       string
+		filter     *OpsOpenAITokenStatsFilter
+		wantCode   int
+		wantReason string
+	}{
+		{
+			name:       "filter 不能为空",
+			filter:     nil,
+			wantCode:   400,
+			wantReason: "OPS_FILTER_REQUIRED",
+		},
+		{
+			name: "start_time/end_time 必填",
+			filter: &OpsOpenAITokenStatsFilter{
+				StartTime: time.Time{},
+				EndTime:   now,
+			},
+			wantCode:   400,
+			wantReason: "OPS_TIME_RANGE_REQUIRED",
+		},
+		{
+			name: "start_time 不能晚于 end_time",
+			filter: &OpsOpenAITokenStatsFilter{
+				StartTime: now,
+				EndTime:   now.Add(-1 * time.Minute),
+			},
+			wantCode:   400,
+			wantReason: "OPS_TIME_RANGE_INVALID",
+		},
+		{
+			name: "group_id 必须大于 0",
+			filter: &OpsOpenAITokenStatsFilter{
+				StartTime: now.Add(-time.Hour),
+				EndTime:   now,
+				GroupID:   int64Ptr(0),
+			},
+			wantCode:   400,
+			wantReason: "OPS_GROUP_ID_INVALID",
+		},
+		{
+			name: "top_n 与分页参数互斥",
+			filter: &OpsOpenAITokenStatsFilter{
+				StartTime: now.Add(-time.Hour),
+				EndTime:   now,
+				TopN:      10,
+				Page:      1,
+			},
+			wantCode:   400,
+			wantReason: "OPS_PAGINATION_CONFLICT",
+		},
+		{
+			name: "top_n 参数越界",
+			filter: &OpsOpenAITokenStatsFilter{
+				StartTime: now.Add(-time.Hour),
+				EndTime:   now,
+				TopN:      101,
+			},
+			wantCode:   400,
+			wantReason: "OPS_TOPN_INVALID",
+		},
+		{
+			name: "page_size 参数越界",
+			filter: &OpsOpenAITokenStatsFilter{
+				StartTime: now.Add(-time.Hour),
+				EndTime:   now,
+				Page:      1,
+				PageSize:  101,
+			},
+			wantCode:   400,
+			wantReason: "OPS_PAGE_SIZE_INVALID",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			svc := &OpsService{
+				opsRepo: &openAITokenStatsRepoStub{},
+			}
+
+			_, err := svc.GetOpenAITokenStats(context.Background(), tt.filter)
+			require.Error(t, err)
+			require.Equal(t, tt.wantCode, infraerrors.Code(err))
+			require.Equal(t, tt.wantReason, infraerrors.Reason(err))
+		})
+	}
+}
+
+func TestOpsServiceGetOpenAITokenStats_DefaultPagination(t *testing.T) {
+	now := time.Now().UTC()
+	repo := &openAITokenStatsRepoStub{
+		resp: &OpsOpenAITokenStatsResponse{
+			Items: []*OpsOpenAITokenStatsItem{
+				{Model: "gpt-4o-mini", RequestCount: 10},
+			},
+			Total: 1,
+		},
+	}
+	svc := &OpsService{opsRepo: repo}
+
+	filter := &OpsOpenAITokenStatsFilter{
+		TimeRange: "30d",
+		StartTime: now.Add(-30 * 24 * time.Hour),
+		EndTime:   now,
+	}
+	resp, err := svc.GetOpenAITokenStats(context.Background(), filter)
+	require.NoError(t, err)
+	require.NotNil(t, resp)
+	require.NotNil(t, repo.captured)
+	require.Equal(t, 1, repo.captured.Page)
+	require.Equal(t, 20, repo.captured.PageSize)
+	require.Equal(t, 0, repo.captured.TopN)
+}
+
+func TestOpsServiceGetOpenAITokenStats_RepoUnavailable(t *testing.T) {
+	now := time.Now().UTC()
+	svc := &OpsService{}
+
+	_, err := svc.GetOpenAITokenStats(context.Background(), &OpsOpenAITokenStatsFilter{
+		TimeRange: "1h",
+		StartTime: now.Add(-time.Hour),
+		EndTime:   now,
+		TopN:      10,
+	})
+	require.Error(t, err)
+	require.Equal(t, 503, infraerrors.Code(err))
+	require.Equal(t, "OPS_REPO_UNAVAILABLE", infraerrors.Reason(err))
+}
+
+func int64Ptr(v int64) *int64 { return &v }