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/styles/calendar.css

@@ -555,19 +555,6 @@
   transform: scale(1.1);
 }
 
-/* Allday-Toggle */
-.allday-toggle {
-  display: flex;
-  align-items: center;
-  gap: var(--space-3);
-  cursor: pointer;
-}
-
-.allday-toggle__label {
-  font-size: var(--text-sm);
-  color: var(--color-text-primary);
-}
-
 /* --------------------------------------------------------
  * Termin-Detailansicht (Popup beim Klick)
  * -------------------------------------------------------- */