feat: add paginated travel export endpoint for the teamer app

GET /api/travels/export flattens the XML export into one row per travel
date x hotel with its pickups resolved, so the Teamer app can import the
disposition in one walk instead of fanning out over /api/travels.

Built from the XML file map, not travel_snapshot: the snapshot table sits
at this grain but refreshes on its own schedule, while the loaders share
the bpn.cache pool under the xml-sync tag. That is what makes /api/hotels,
/api/pickups and this export move together for free.

Each Ziel_*.xml is walked once and TravelParser::getPickups() does the
zeit parsing, which buys both zeit shapes and adjustOvernightTimes() --
a time-only 02:15 listed after a 23:59 rolls onto the next calendar day.
Pickups join against PickupLoader::loadAll() rather than
patchPickupsDetails(), which sorts: the contract is source order.

The whole assembled export is cached, not a page, so skipped, total and
pickupsWithoutMasterData are whole-export figures identical on every page
and a consumer can abort after the first one. Errors stay real status
codes; the builder is deliberately not wrapped in a catch that would
answer 200 with an error body the way hotelAvailability() does.

The route is declared before api_travel_single_code and that route grows
a requirement, or /api/travels/export resolves to byCode('export') and
404s as though the endpoint existed with no data.

Co-Authored-By: Claude Opus 5 <[email protected]>

src/Model/TravelExportQuery.php

@@ -0,0 +1,19 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Model;
+
+use Symfony\Component\Validator\Constraints as Assert;
+
+final readonly class TravelExportQuery
+{
+    public function __construct(
+        #[Assert\Positive]
+        public int $page = 1,
+
+        #[Assert\Range(min: 1, max: 1000)]
+        public int $perPage = 500,
+    ) {
+    }
+}