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

server/src/db/migrations.ts

@@ -321,6 +321,10 @@ function runMigrations(db: Database.Database): void {
         UNIQUE(file_id, place_id)
       )`);
     },
+    () => {
+      // Add day_plan_position to reservations for persistent transport ordering in day timeline
+      try { db.exec('ALTER TABLE reservations ADD COLUMN day_plan_position REAL DEFAULT NULL'); } catch {}
+    },
   ];
 
   if (currentVersion < migrations.length) {