adjust panel iot page to match dashboard-cpsp page

utils/format.ts

@@ -57,6 +57,34 @@ export function inclusiveDayCount(startIso: string, endIso: string): number {
   return Math.max(1, cycleDayForDate(startIso, endIso) + 1);
 }
 
+/** Inclusive upper date for open cycles (null end_date) without producing NaN day math. */
+export function resolveCycleBoundDate(cycle: {
+  start_date: string;
+  end_date?: string | null;
+  soft_end_date?: string | null;
+  visible_through_date?: string | null;
+  total_days?: number;
+}): string {
+  if (cycle.end_date) return cycle.end_date;
+  if (cycle.soft_end_date) return cycle.soft_end_date;
+  if (cycle.visible_through_date) return cycle.visible_through_date;
+  if (cycle.total_days != null && cycle.total_days > 0) {
+    return addDaysIso(cycle.start_date, Math.max(cycle.total_days - 1, 0));
+  }
+  return todayIso();
+}
+
+/** 0-based last day index from start → bound date (safe when end_date is null). */
+export function cycleLastDayIndex(cycle: {
+  start_date: string;
+  end_date?: string | null;
+  soft_end_date?: string | null;
+  visible_through_date?: string | null;
+  total_days?: number;
+}): number {
+  return cycleDayForDate(cycle.start_date, resolveCycleBoundDate(cycle));
+}
+
 export type CycleStatusUi = 'active' | 'pending_close' | 'closed';
 
 export function resolveCycleStatus(cycle: {