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/handler/admin/ops_dashboard_handler.go

@@ -1,6 +1,7 @@
 package admin
 
 import (
+	"fmt"
 	"net/http"
 	"strconv"
 	"strings"
@@ -218,6 +219,115 @@ func (h *OpsHandler) GetDashboardErrorDistribution(c *gin.Context) {
 	response.Success(c, data)
 }
 
+// GetDashboardOpenAITokenStats returns OpenAI token efficiency stats grouped by model.
+// GET /api/v1/admin/ops/dashboard/openai-token-stats
+func (h *OpsHandler) GetDashboardOpenAITokenStats(c *gin.Context) {
+	if h.opsService == nil {
+		response.Error(c, http.StatusServiceUnavailable, "Ops service not available")
+		return
+	}
+	if err := h.opsService.RequireMonitoringEnabled(c.Request.Context()); err != nil {
+		response.ErrorFrom(c, err)
+		return
+	}
+
+	filter, err := parseOpsOpenAITokenStatsFilter(c)
+	if err != nil {
+		response.BadRequest(c, err.Error())
+		return
+	}
+
+	data, err := h.opsService.GetOpenAITokenStats(c.Request.Context(), filter)
+	if err != nil {
+		response.ErrorFrom(c, err)
+		return
+	}
+	response.Success(c, data)
+}
+
+func parseOpsOpenAITokenStatsFilter(c *gin.Context) (*service.OpsOpenAITokenStatsFilter, error) {
+	if c == nil {
+		return nil, fmt.Errorf("invalid request")
+	}
+
+	timeRange := strings.TrimSpace(c.Query("time_range"))
+	if timeRange == "" {
+		timeRange = "30d"
+	}
+	dur, ok := parseOpsOpenAITokenStatsDuration(timeRange)
+	if !ok {
+		return nil, fmt.Errorf("invalid time_range")
+	}
+	end := time.Now().UTC()
+	start := end.Add(-dur)
+
+	filter := &service.OpsOpenAITokenStatsFilter{
+		TimeRange: timeRange,
+		StartTime: start,
+		EndTime:   end,
+		Platform:  strings.TrimSpace(c.Query("platform")),
+	}
+
+	if v := strings.TrimSpace(c.Query("group_id")); v != "" {
+		id, err := strconv.ParseInt(v, 10, 64)
+		if err != nil || id <= 0 {
+			return nil, fmt.Errorf("invalid group_id")
+		}
+		filter.GroupID = &id
+	}
+
+	topNRaw := strings.TrimSpace(c.Query("top_n"))
+	pageRaw := strings.TrimSpace(c.Query("page"))
+	pageSizeRaw := strings.TrimSpace(c.Query("page_size"))
+	if topNRaw != "" && (pageRaw != "" || pageSizeRaw != "") {
+		return nil, fmt.Errorf("invalid query: top_n cannot be used with page/page_size")
+	}
+
+	if topNRaw != "" {
+		topN, err := strconv.Atoi(topNRaw)
+		if err != nil || topN < 1 || topN > 100 {
+			return nil, fmt.Errorf("invalid top_n")
+		}
+		filter.TopN = topN
+		return filter, nil
+	}
+
+	filter.Page = 1
+	filter.PageSize = 20
+	if pageRaw != "" {
+		page, err := strconv.Atoi(pageRaw)
+		if err != nil || page < 1 {
+			return nil, fmt.Errorf("invalid page")
+		}
+		filter.Page = page
+	}
+	if pageSizeRaw != "" {
+		pageSize, err := strconv.Atoi(pageSizeRaw)
+		if err != nil || pageSize < 1 || pageSize > 100 {
+			return nil, fmt.Errorf("invalid page_size")
+		}
+		filter.PageSize = pageSize
+	}
+	return filter, nil
+}
+
+func parseOpsOpenAITokenStatsDuration(v string) (time.Duration, bool) {
+	switch strings.TrimSpace(v) {
+	case "30m":
+		return 30 * time.Minute, true
+	case "1h":
+		return time.Hour, true
+	case "1d":
+		return 24 * time.Hour, true
+	case "15d":
+		return 15 * 24 * time.Hour, true
+	case "30d":
+		return 30 * 24 * time.Hour, true
+	default:
+		return 0, false
+	}
+}
+
 func pickThroughputBucketSeconds(window time.Duration) int {
 	// Keep buckets predictable and avoid huge responses.
 	switch {