feat: support multi-day spanning for reservations (flights, rental cars, events)

- ReservationModal: add separate departure/arrival date+time fields with
  type-specific labels (Departure/Arrival for flights, Pickup/Return for
  cars, Start/End for generic types), timezone fields for flights
- DayPlanSidebar: getTransportForDay now matches reservations across all
  days in their date range; shows phase badges (Departure/In Transit/
  Arrival etc.) with appropriate time display per day
- ReservationsPanel: show date range when end date differs from start
- All 13 translation files updated with new keys

client/src/components/Planner/ReservationsPanel.tsx

@@ -136,7 +136,12 @@ function ReservationCard({ r, tripId, onEdit, onDelete, files = [], onNavigateTo
               {r.reservation_time && (
                 <div style={{ flex: 1, padding: '5px 10px', textAlign: 'center', borderRight: '1px solid var(--border-faint)' }}>
                   <div style={{ fontSize: 9, fontWeight: 600, color: 'var(--text-faint)', textTransform: 'uppercase', letterSpacing: '0.03em' }}>{t('reservations.date')}</div>
-                  <div style={{ fontSize: 11, fontWeight: 600, color: 'var(--text-primary)', marginTop: 1 }}>{fmtDate(r.reservation_time)}</div>
+                  <div style={{ fontSize: 11, fontWeight: 600, color: 'var(--text-primary)', marginTop: 1 }}>
+                    {fmtDate(r.reservation_time)}
+                    {r.reservation_end_time?.includes('T') && r.reservation_end_time.split('T')[0] !== r.reservation_time.split('T')[0] && (
+                      <> – {fmtDate(r.reservation_end_time)}</>
+                    )}
+                  </div>
                 </div>
               )}
               {r.reservation_time?.includes('T') && (