refactor: generatePlan returns {assignments, skippedDates}

js/calendar.js

@@ -98,7 +98,8 @@ export function renderCalendar() {
       state.calendar.holidays, state.calendar.companyClosures);
     const prefix = currentYear + '-' + String(currentMonth).padStart(2,'0');
     const historyWithoutMonth = state.history.filter(h => !h.date.startsWith(prefix));
-    currentPlan = generatePlan(workdays, state.employees, historyWithoutMonth);
+    const result = generatePlan(workdays, state.employees, historyWithoutMonth);
+    currentPlan = result.assignments;
     addHistoryEntries(state, currentPlan);
     saveState();
     renderGrid(wrapper, exportBtn);