fix(airports): keep airports OurAirports flags as having no scheduled service

The airport picker never offered Little Cayman (LYB): OurAirports marks it as
having no scheduled service although it has daily flights, and the build
dropped every airport on that flag. The same flag also hid Vestmannaeyjar,
Western Sydney and around 1,280 other large and medium airports with an IATA
code. The build now applies the flag to small airports only, where it keeps
private airstrips out.

The bundled list gains exactly those airports. Every entry it already carried
stays unchanged, because a fresh OurAirports export currently renames PBI to
DJT and drops nine other codes that saved bookings point at.

Closes #2820

server/scripts/build-airports.mjs

@@ -1,6 +1,7 @@
 #!/usr/bin/env node
 // Build server/assets/airports.json from OurAirports (davidmegginson.github.io/ourairports-data).
-// License: Public Domain. Keeps large/medium airports with an IATA code; timezone derived from coords via tz-lookup.
+// License: Public Domain. Keeps large/medium airports with an IATA code, small ones only with scheduled service;
+// timezone derived from coords via tz-lookup.
 import fs from 'node:fs';
 import https from 'node:https';
 import path from 'node:path';
@@ -91,7 +92,9 @@ for (let i = 1; i < rows.length; i++) {
   if (!KEEP.has(r[TYPE])) continue;
   const iata = r[IATA]?.trim().toUpperCase();
   if (!iata || iata.length !== 3) continue;
-  if (r[SERVICE] !== 'yes') continue;
+  // The scheduled_service flag lags reality: Little Cayman (LYB) has daily flights and is
+  // marked "no". So it only filters the small fields, where it keeps every airstrip with a code out.
+  if (r[TYPE] === 'small_airport' && r[SERVICE] !== 'yes') continue;
   const lat = Number(r[LAT]);
   const lng = Number(r[LNG]);
   if (!Number.isFinite(lat) || !Number.isFinite(lng)) continue;

server/tests/unit/nest/airports/airports.asset.test.ts

@@ -0,0 +1,23 @@
+/**
+ * The bundled assets/airports.json itself, not a fixture.
+ *
+ * OurAirports marks some airports with daily flights as having no scheduled
+ * service, and the build used to drop them on that flag alone (#2820, Little
+ * Cayman). These pin a few of them and the codes saved bookings already point at.
+ */
+import { findByIata } from '../../../../src/nest/airports/airports.data';
+
+import { describe, it, expect } from 'vitest';
+
+describe('bundled airport dataset', () => {
+  it('AIRPORT-ASSET-001: keeps airports OurAirports flags as unscheduled', () => {
+    expect(findByIata('LYB')?.name).toBe('Edward Bodden Little Cayman Airfield');
+    expect(findByIata('VEY')?.country).toBe('IS');
+  });
+
+  it('AIRPORT-ASSET-002: still resolves the codes it carried before', () => {
+    for (const code of ['PBI', 'ADA', 'GCM', 'CYB', 'FRA']) {
+      expect(findByIata(code), code).not.toBeNull();
+    }
+  });
+});