feat: add UI/UX polish with navigation rail, confirm dialogs, welcome banner, and form validation

- Add NavigationRail component (desktop vertical icon sidebar + mobile bottom tab bar)
- Add ConfirmDialog with promise-based useConfirmDialog hook for async confirmation flow
- Add WelcomeBanner onboarding component (one-time display, localStorage persistence)
- Polish login form UX (shake on error, TOTP slide animation, password visibility toggle, session expired banner)
- Add inline form validation with shake animation in email composer and contacts
- Add empty state patterns for contacts (no data vs no search results with contextual actions)
- Improve toast notification system with undo action support and typed durations
- Add WCAG AA prefers-reduced-motion media query, safe area insets, sr-only live regions
- Add template settings tab and keyboard shortcut integration
- Update all 8 locale translations

components/settings/vacation-settings.tsx

@@ -62,7 +62,9 @@ export function VacationSettings() {
       warnings.push(t('warnings.end_before_start'));
     }
 
-    if (localFromDate && new Date(localFromDate) < new Date()) {
+    const todayStart = new Date();
+    todayStart.setHours(0, 0, 0, 0);
+    if (localFromDate && new Date(localFromDate) < todayStart) {
       warnings.push(t('warnings.start_in_past'));
     }