ScheduleStartPage: add departure===arrival same-cities validation (Angular parity)

src/features/schedule/components/ScheduleStartPage.tsx

@@ -129,6 +129,11 @@ export const ScheduleStartPage: FC = () => {
   const scheduleMinDate = useRef(getScheduleMinDate()).current;
   const scheduleMaxDate = useRef(getScheduleMaxDate()).current;
 
+  // Same-cities validation mirrors ScheduleFilter (Angular's
+  // ScheduleFilterValidationService): reject departure === arrival with
+  // the shared translation key.
+  const [sameCitiesError, setSameCitiesError] = useState<string | null>(null);
+
   const handleSubmit = useCallback(
     (e: FormEvent) => {
       e.preventDefault();
@@ -137,6 +142,12 @@ export const ScheduleStartPage: FC = () => {
       const arr = arrivalCode.trim().toUpperCase();
       if (!dep || !arr) return;
 
+      if (dep === arr) {
+        setSameCitiesError("SHARED.ARRIVAL-EQUALS-DEPARTURE-ERROR");
+        return;
+      }
+      setSameCitiesError(null);
+
       // Empty dates default to the current week (today → today + 7) so
       // the search proceeds even when the user leaves the placeholder
       // untouched. Mirrors Angular's "by default it's the current week"
@@ -222,7 +233,10 @@ export const ScheduleStartPage: FC = () => {
         label={t("SHARED.DEPARTURE_CITY")}
         placeholder={t("SHARED.CITY_PLACEHOLDER")}
         value={departureCode}
-        onChange={setDepartureCode}
+        onChange={(code) => {
+          setDepartureCode(code);
+          if (sameCitiesError) setSameCitiesError(null);
+        }}
         dictionaries={dictionaries}
         testIdPrefix="schedule-departure"
       />
@@ -248,10 +262,21 @@ export const ScheduleStartPage: FC = () => {
         label={t("SHARED.ARRIVAL_CITY")}
         placeholder={t("SHARED.CITY_PLACEHOLDER")}
         value={arrivalCode}
-        onChange={setArrivalCode}
+        onChange={(code) => {
+          setArrivalCode(code);
+          if (sameCitiesError) setSameCitiesError(null);
+        }}
         dictionaries={dictionaries}
         testIdPrefix="schedule-arrival"
       />
+      {sameCitiesError && (
+        <div
+          className="validation-tooltip"
+          data-testid="schedule-same-cities-error"
+        >
+          {t(sameCitiesError)}
+        </div>
+      )}
 
       <div className="schedule-start__field">
         <label htmlFor="schedule-date-from">{t("SHARED.SCHEDULES_DATE")}</label>