Configure dev proxy to flights.test.aeroflot.ru and fix API endpoint paths

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.

src/shared/api/client.ts

@@ -22,7 +22,7 @@ const DEFAULT_RETRY_STATUS_CODES = [408, 429, 500, 502, 503, 504];
 
 export class ApiClient {
   private readonly baseUrl: string;
-  private readonly locale: Language;
+  readonly locale: Language;
   private readonly traceId: string | undefined;
   private readonly fetchFn: typeof fetch;
   private readonly timeoutMs: number;