fix(icalendar): Handle non-string rrule property gracefully

icalendar.ts

@@ -154,6 +154,11 @@ export function expandRecurrences(icsEvent: any, windowDays = 365): any[] {
   const rruleStr = icsEvent.rrule || (icsEvent as any).recurrenceRule;
   if (!rruleStr) return [icsEvent];
 
+  if (typeof rruleStr !== "string") {
+    console.warn(`[iCalendar] Invalid rrule type (${typeof rruleStr}) for event "${icsEvent.summary || "Untitled"}". Treating as non-recurring.`);
+    return [icsEvent];
+  }
+
   try {
     const set = new RRuleSet();
     const cleanRule = rruleStr.replace(/^RRULE:/i, "");