fix(ux): improve microinteractions across the app

1. Nav-item tap: smooth scale transition instead of abrupt snap
2. Custom toggle switch: iOS-style toggle replaces native checkboxes
3. Focus-visible: outline on cards, buttons, FABs for keyboard users
4. Empty-state: gentle fade-in animation
5. Toast icons: SVG icons for success/danger/warning types
6. Swipe haptic: vibrate(15) fires at threshold during touchmove

public/pages/calendar.js

@@ -795,9 +795,10 @@ function buildEventModalContent({ mode, event, date }) {
     </div>
 
     <div class="form-group">
-      <label class="allday-toggle">
+      <label class="toggle">
         <input type="checkbox" id="modal-allday" ${isEdit && event.all_day ? 'checked' : ''}>
-        <span class="allday-toggle__label">${t('calendar.allDayToggle')}</span>
+        <span class="toggle__track"></span>
+        <span>${t('calendar.allDayToggle')}</span>
       </label>
     </div>