feat: auto-persist state to localStorage on every change

js/app.js

@@ -2,6 +2,8 @@ import { renderEmployees } from './employees.js';
 import { renderCalendar } from './calendar.js';
 import { renderDataTab } from './history.js';
 
+const STORAGE_KEY = 'morning-planner-state';
+
 // Shared mutable state — imported by all other modules
 export const state = {
   employees: [],
@@ -9,6 +11,32 @@ export const state = {
   history: []
 };
 
+// Load persisted state from localStorage on startup
+try {
+  const saved = localStorage.getItem(STORAGE_KEY);
+  if (saved) {
+    const parsed = JSON.parse(saved);
+    if (Array.isArray(parsed.employees)) state.employees = parsed.employees;
+    if (parsed.calendar) state.calendar = parsed.calendar;
+    if (Array.isArray(parsed.history)) state.history = parsed.history;
+  }
+} catch {
+  // Corrupt storage — start fresh
+}
+
+// Call after any state mutation to persist automatically
+export function saveState() {
+  try {
+    localStorage.setItem(STORAGE_KEY, JSON.stringify({
+      employees: state.employees,
+      calendar: state.calendar,
+      history: state.history
+    }));
+  } catch {
+    // Storage full or unavailable — silently ignore
+  }
+}
+
 // Tab switching
 document.querySelectorAll('.tab-btn').forEach(btn => {
   btn.addEventListener('click', () => {