fix(planner): keep a parked car off the days between drop-off and pickup

A parking booking spanning the trip showed up on every day, sometimes in between
planned activities. It now appears on its first and last day only, with drop-off
and pickup wording, and contributes nothing to the days in between, not even a
badge in the day header. Applied to the day plan, the mobile timeline, the PDF
export and the shared trip view, so a shared link shows what the app shows.

Rental cars stay as they are. The report names the car's smaller tag as the thing
it does not want for parking, not as something to change, and a car's middle days
move into the day header, which is what people expect from a vehicle they are
driving around.

The distance connector between legs is keyed off the row that gets hidden, so
hiding it naively takes the "2 km" label with it, which is what #1504 was about.
There is a test that fails without that guard.

Each segment of a stopover flight or train can also carry its own booking
reference now, since airlines often issue one per flight rather than one per
booking. Legs already live as a JSON array on the reservation, so this is an
optional field per entry: no migration, no contract change, and a booking without
it renders exactly as before. Readable everywhere it can be entered, desktop and
mobile, through the same blur treatment other booking codes get, plus the PDF and
the calendar description. create_transport and update_transport preserve it too,
otherwise they would accept the field and silently drop it.

Closes #1937
Closes #1943

server/src/nest/calendar/calendar.service.ts

@@ -412,6 +412,14 @@ export class CalendarService {
         // Multi-leg flight: show the whole route (FRA → BER → HND) on one event.
         const stops = [meta.legs[0]?.from, ...meta.legs.map((l: { to?: string }) => l.to)].filter(Boolean);
         if (stops.length) desc += `\nRoute: ${stops.join(' → ')}`;
+        // A segment booked under its own reference gets its own line (#1943): at
+        // the gate it is that code the airline asks for, not the booking's. No
+        // leg reference, no extra line, so an existing feed stays byte-identical.
+        for (const leg of meta.legs as { from?: string; to?: string; confirmation_number?: string }[]) {
+          if (!leg.confirmation_number) continue;
+          const segment = [leg.from, leg.to].filter(Boolean).join('-');
+          desc += `\nConfirmation${segment ? ` ${segment}` : ''}: ${leg.confirmation_number}`;
+        }
       } else if (meta.departure_airport || meta.arrival_airport) {
         if (meta.departure_airport) desc += `\nFrom: ${meta.departure_airport}`;
         if (meta.arrival_airport) desc += `\nTo: ${meta.arrival_airport}`;