feat: show transport bookings in day plan timeline — closes #37

Transport reservations (flights, trains, buses, cars, cruises) now appear
directly in the day plan timeline based on their reservation date/time.

- Transport cards display inline with places and notes, sorted by time
- Click to open detail modal with all booking data and linked files
- Persistent positioning via new day_plan_position field on reservations
- Free drag & drop: places can be moved between/around transport entries
- Arrow reorder works on the full visual list including transports
- Timed places show confirmation popup when reorder breaks chronology
- Custom delete confirmation popup for reservations
- DB migration adds day_plan_position column to reservations table
- New batch endpoint PUT /reservations/positions for position updates
- i18n keys added for DE and EN

client/src/api/client.ts

@@ -207,6 +207,7 @@ export const reservationsApi = {
   create: (tripId: number | string, data: Record<string, unknown>) => apiClient.post(`/trips/${tripId}/reservations`, data).then(r => r.data),
   update: (tripId: number | string, id: number, data: Record<string, unknown>) => apiClient.put(`/trips/${tripId}/reservations/${id}`, data).then(r => r.data),
   delete: (tripId: number | string, id: number) => apiClient.delete(`/trips/${tripId}/reservations/${id}`).then(r => r.data),
+  updatePositions: (tripId: number | string, positions: { id: number; day_plan_position: number }[]) => apiClient.put(`/trips/${tripId}/reservations/positions`, { positions }).then(r => r.data),
 }
 
 export const weatherApi = {