Root cause of search not working: globalThis.fetch stored as a class
field loses its Window binding, causing 'Illegal invocation'. Fixed
with fetch.bind(globalThis).
Also fix calendar days endpoint date format from yyyyMMdd to
yyyy-MM-ddT00:00:00 matching Angular's ApiFormatterService.
API functions now build the full localized path matching the Angular
EndpointService pattern (/api/flights/{version}/{locale}/{endpoint}).
The dev proxy forwards /api and /flights to the test backend.
gnezim