feat: show current-cycle daily token peak

backend/CONTRACT.md

@@ -39,7 +39,7 @@
  fetchedAt, stale, lastError?}
 ```
 
-时间字段为 Unix 秒。`currentCycle` 是按当前仍有效的最长限额窗口计算的当前重置周期；`totalTokens` 由 `account/usage/read` 的每日 Token bucket 汇总，受每日粒度影响，无法精确切分周期起止日期内的单日数据。没有有效窗口或用量接口失败时省略该字段。app-server 未提供的摘要字段可以是 `null`；列表应返回数组而非 `null`。
+时间字段为 Unix 秒。`currentCycle` 是按当前仍有效的最长限额窗口计算的当前重置周期；`totalTokens` 由 `account/usage/read` 的每日 Token bucket 汇总，受每日粒度影响，无法精确切分周期起止日期内的单日数据。`summary.peakDailyTokens` 是同一当前重置周期内每日 Token bucket 的最大值，不再直接采用 app-server 未限定口径的峰值摘要；没有有效窗口或周期内没有每日数据时为 `null`。app-server 未提供的其他摘要字段可以是 `null`；列表应返回数组而非 `null`。
 
 ## 3. 系统、初始化与会话
 

backend/internal/app/api.go

@@ -533,6 +533,7 @@ func (a *App) syncAccount(ctx context.Context, id int64) error {
 			_, _ = a.store.DB.Exec("INSERT INTO daily_usage(account_id,date,total_tokens,fetched_at) VALUES(?,?,?,?) ON CONFLICT(account_id,date) DO UPDATE SET total_tokens=excluded.total_tokens,fetched_at=excluded.fetched_at", id, x.StartDate, x.Tokens, d.FetchedAt)
 		}
 		d.CurrentCycle = currentTokenCycle(d.Limits, d.Usage, d.FetchedAt)
+		d.Summary.PeakDailyTokens = peakDailyTokensForCycle(d.CurrentCycle, d.Usage, d.FetchedAt)
 	}
 	resetDetected, e := a.storeLimitSnapshots(d)
 	if e != nil {
@@ -642,6 +643,29 @@ func currentTokenCycle(limits []LimitBucket, usage []UsagePoint, fetchedAt int64
 	}
 }
 
+func peakDailyTokensForCycle(cycle *TokenCycle, usage []UsagePoint, fetchedAt int64) *int64 {
+	if cycle == nil {
+		return nil
+	}
+	startDate := time.Unix(cycle.StartedAt, 0).UTC().Format("2006-01-02")
+	endDate := time.Unix(fetchedAt, 0).UTC().Format("2006-01-02")
+	var peak int64
+	found := false
+	for _, point := range usage {
+		if _, err := time.Parse("2006-01-02", point.Date); err != nil || point.Date < startDate || point.Date > endDate {
+			continue
+		}
+		if !found || point.TotalTokens > peak {
+			peak = point.TotalTokens
+			found = true
+		}
+	}
+	if !found {
+		return nil
+	}
+	return &peak
+}
+
 func betterTokenCycleLimit(candidate, current LimitBucket) bool {
 	if candidate.WindowDurationMinutes != current.WindowDurationMinutes {
 		return candidate.WindowDurationMinutes > current.WindowDurationMinutes

backend/internal/app/runtime_test.go

@@ -331,6 +331,24 @@ func TestCurrentTokenCycleRequiresAValidFutureResetWindow(t *testing.T) {
 	}
 }
 
+func TestPeakDailyTokensUsesOnlyTheCurrentTokenCycle(t *testing.T) {
+	now := time.Date(2026, time.August, 14, 12, 0, 0, 0, time.UTC)
+	cycle := &TokenCycle{
+		StartedAt: time.Date(2026, time.August, 8, 0, 0, 0, 0, time.UTC).Unix(),
+		ResetsAt:  time.Date(2026, time.August, 15, 0, 0, 0, 0, time.UTC).Unix(),
+	}
+	peak := peakDailyTokensForCycle(cycle, []UsagePoint{
+		{Date: "2026-08-07", TotalTokens: 900},
+		{Date: "2026-08-08", TotalTokens: 100},
+		{Date: "2026-08-10", TotalTokens: 200},
+		{Date: "2026-08-14", TotalTokens: 300},
+		{Date: "2026-08-15", TotalTokens: 800},
+	}, now.Unix())
+	if peak == nil || *peak != 300 {
+		t.Fatalf("cycle peak = %v; want 300", peak)
+	}
+}
+
 func TestFlattenLimitReadsAppServerWindowDuration(t *testing.T) {
 	var limit rawLimit
 	if err := json.Unmarshal([]byte(`{