Clean unused helpers after details-page simplification

- ScheduleDetailsPage: drop shiftYmd helper and selectedYmd local —
  both were left over from the removed day-sibling search path.
- ScheduleFlightBody.test: drop fireEvent import + FUTURE_340D /
  FUTURE_1H / YESTERDAY / todayUtc constants; they belonged to the
  Buy/Status button tests that moved to the summary-header layer.
- flight-details + error-handling integration tests: mock
  useCityName / useStationDisplayName so OnlineBoardDetailsPage can
  render without an ApiClientProvider wrapping — the station lookup
  hooks now transitively depend on useApiClient via the cached
  useDictionaries fetcher introduced in 7deb46a.

tests/integration/online-board/error-handling.test.tsx

@@ -92,6 +92,13 @@ vi.mock("@/shared/hooks/useAppSettings.js", () => ({
   }),
 }));
 
+// OnlineBoardDetailsPage resolves station codes via useStationDisplayName,
+// which internally hits useApiClient — no ApiClientProvider in this tree.
+vi.mock("@/shared/hooks/useDictionaries.js", () => ({
+  useCityName: (code: string) => code,
+  useStationDisplayName: (code: string) => code,
+}));
+
 // ---------------------------------------------------------------------------
 // Constants
 // ---------------------------------------------------------------------------

tests/integration/online-board/flight-details.test.tsx

@@ -71,6 +71,14 @@ vi.mock("@/shared/hooks/useAppSettings.js", () => ({
   }),
 }));
 
+// OnlineBoardDetailsPage resolves station codes via useStationDisplayName,
+// which internally hits useApiClient. There's no ApiClientProvider in
+// this test tree, so stub the name-lookup hooks to echo the code.
+vi.mock("@/shared/hooks/useDictionaries.js", () => ({
+  useCityName: (code: string) => code,
+  useStationDisplayName: (code: string) => code,
+}));
+
 // ---------------------------------------------------------------------------
 // Helpers
 // ---------------------------------------------------------------------------