feat(dashboard): toggle recent usage between tokens and spending

backend/internal/handler/admin/dashboard_handler.go

@@ -500,7 +500,11 @@ func (h *DashboardHandler) GetUserUsageTrend(c *gin.Context) {
 		limit = 12
 	}
 
-	trend, hit, err := h.getUserUsageTrendCached(c.Request.Context(), startTime, endTime, granularity, limit)
+	metric := c.DefaultQuery("metric", "tokens")
+	if metric != "tokens" && metric != "actual_cost" {
+		metric = "tokens"
+	}
+	trend, hit, err := h.getUserUsageTrendCached(c.Request.Context(), startTime, endTime, granularity, limit, metric)
 	if err != nil {
 		response.Error(c, 500, "Failed to get user usage trend")
 		return

backend/internal/handler/admin/dashboard_handler_cache_test.go

@@ -45,6 +45,7 @@ func (r *dashboardUsageRepoCacheProbe) GetUserUsageTrend(
 	startTime, endTime time.Time,
 	granularity string,
 	limit int,
+	metric string,
 ) ([]usagestats.UserUsageTrendPoint, error) {
 	r.usersTrendCalls.Add(1)
 	return []usagestats.UserUsageTrendPoint{{
@@ -115,4 +116,20 @@ func TestDashboardHandler_GetUserUsageTrend_UsesCache(t *testing.T) {
 	require.Equal(t, http.StatusOK, rec2.Code)
 	require.Equal(t, "hit", rec2.Header().Get("X-Snapshot-Cache"))
 	require.Equal(t, int32(1), repo.usersTrendCalls.Load())
+
+	for _, tc := range []struct {
+		metric, cache string
+		calls         int32
+	}{
+		{"actual_cost", "miss", 2},
+		{"actual_cost", "hit", 2},
+		{"tokens", "hit", 2},
+	} {
+		req := httptest.NewRequest(http.MethodGet, "/admin/dashboard/users-trend?start_date=2026-03-01&end_date=2026-03-07&granularity=day&limit=8&metric="+tc.metric, nil)
+		rec := httptest.NewRecorder()
+		router.ServeHTTP(rec, req)
+		require.Equal(t, http.StatusOK, rec.Code)
+		require.Equal(t, tc.cache, rec.Header().Get("X-Snapshot-Cache"))
+		require.Equal(t, tc.calls, repo.usersTrendCalls.Load())
+	}
 }

backend/internal/handler/admin/dashboard_query_cache.go

@@ -53,6 +53,7 @@ type dashboardEntityTrendCacheKey struct {
 	EndTime     string `json:"end_time"`
 	Granularity string `json:"granularity"`
 	Limit       int    `json:"limit"`
+	Metric      string `json:"metric,omitempty"`
 }
 
 func cacheStatusValue(hit bool) string {
@@ -213,15 +214,16 @@ func (h *DashboardHandler) getAPIKeyUsageTrendCached(ctx context.Context, startT
 	return trend, hit, err
 }
 
-func (h *DashboardHandler) getUserUsageTrendCached(ctx context.Context, startTime, endTime time.Time, granularity string, limit int) ([]usagestats.UserUsageTrendPoint, bool, error) {
+func (h *DashboardHandler) getUserUsageTrendCached(ctx context.Context, startTime, endTime time.Time, granularity string, limit int, metric string) ([]usagestats.UserUsageTrendPoint, bool, error) {
 	key := mustMarshalDashboardCacheKey(dashboardEntityTrendCacheKey{
 		StartTime:   startTime.UTC().Format(time.RFC3339),
 		EndTime:     endTime.UTC().Format(time.RFC3339),
 		Granularity: granularity,
 		Limit:       limit,
+		Metric:      metric,
 	})
 	entry, hit, err := dashboardUsersTrendCache.GetOrLoad(key, func() (any, error) {
-		return h.dashboardService.GetUserUsageTrend(ctx, startTime, endTime, granularity, limit)
+		return h.dashboardService.GetUserUsageTrend(ctx, startTime, endTime, granularity, limit, metric)
 	})
 	if err != nil {
 		return nil, hit, err

backend/internal/handler/admin/dashboard_snapshot_v2_handler.go

@@ -243,7 +243,7 @@ func (h *DashboardHandler) buildSnapshotV2Response(
 	}
 
 	if includeUsersTrend {
-		usersTrend, _, err := h.getUserUsageTrendCached(ctx, startTime, endTime, granularity, usersTrendLimit)
+		usersTrend, _, err := h.getUserUsageTrendCached(ctx, startTime, endTime, granularity, usersTrendLimit, "tokens")
 		if err != nil {
 			return nil, errors.New("failed to get user usage trend")
 		}