Port Angular's closest-flight auto-select + scroll-into-view behavior

Angular's route/departure/arrival search result list picks a 'current
flight' on load and auto-expands + scrolls it into view — the flight
whose dep/arr time is closest to 'now' for today's searches, or the
first/last flight when the search is for a future/past day. React was
always rendering the list scrolled to the top, so on today's route
search the user sees flights from 00:30 onwards instead of landing on
whatever is departing right now.

- Add features/online-board/closestFlight.ts with a React-flavored port
  of find-closest-flight.ts (plus a today-guard that reuses the same
  'yyyymmdd' shape the URL parser produces).
- FlightList takes an optional initialCurrentFlightId, attaches a ref
  to each card, and scrollIntoView's it on mount / list change.
- FlightCard takes an initialExpanded prop and seeds its useState so
  the selected flight lands expanded, matching the Angular 'expanded:
  true' assignment after setCurrentFlight.
- OnlineBoardSearchPage computes the id via findClosestFlightId using
  the current params (type + date) and forwards it to FlightList.

src/ui/flights/FlightCard.tsx

@@ -25,6 +25,11 @@ export interface FlightCardProps {
    * fires onViewDetails. Matches Angular's board-flight-header behaviour.
    */
   expandable?: boolean;
+  /**
+   * Opens the inline panel on mount — used by the 'closest flight'
+   * auto-selection Angular ships on search results.
+   */
+  initialExpanded?: boolean;
   /** Fired when the user clicks 'Детали рейса' in the expanded panel. */
   onViewDetails?: () => void;
 }
@@ -67,6 +72,7 @@ export const FlightCard: FC<FlightCardProps> = ({
   flight,
   onClick,
   expandable,
+  initialExpanded,
   onViewDetails,
 }) => {
   const { t } = useTranslation();
@@ -85,7 +91,7 @@ export const FlightCard: FC<FlightCardProps> = ({
     departureLeg.equipment?.aircraft?.scheduled?.title ??
     null;
 
-  const [expanded, setExpanded] = useState(false);
+  const [expanded, setExpanded] = useState(Boolean(initialExpanded));
   const rowClickable = expandable || Boolean(onClick);
   const toggleExpanded = (): void => {
     if (expandable) {

src/ui/flights/FlightList.tsx

@@ -1,4 +1,4 @@
-import type { FC } from "react";
+import { type FC, useEffect, useRef } from "react";
 import { useTranslation } from "@/i18n/provider.js";
 import type { ISimpleFlight } from "@/features/online-board/types.js";
 import { FlightCard } from "./FlightCard.js";
@@ -14,6 +14,12 @@ export interface FlightListProps {
   skeletonCount?: number;
   /** Click handler — makes each card act as a link to the details page */
   onFlightClick?: (flight: ISimpleFlight) => void;
+  /**
+   * Id of a flight to auto-expand and scroll into view on mount / list
+   * change. Matches Angular's 'closest flight' behavior (today → closest
+   * to now; other days → first/last).
+   */
+  initialCurrentFlightId?: string | null;
 }
 
 /**
@@ -27,8 +33,20 @@ export const FlightList: FC<FlightListProps> = ({
   loading = false,
   skeletonCount = 5,
   onFlightClick,
+  initialCurrentFlightId,
 }) => {
   const { t } = useTranslation();
+  const cardRefs = useRef<Map<string, HTMLDivElement>>(new Map());
+
+  useEffect(() => {
+    if (!initialCurrentFlightId) return;
+    const el = cardRefs.current.get(initialCurrentFlightId);
+    // jsdom doesn't implement scrollIntoView, so guard the call.
+    if (el && typeof el.scrollIntoView === "function") {
+      el.scrollIntoView({ block: "center", behavior: "smooth" });
+    }
+  }, [initialCurrentFlightId, flights]);
+
   if (loading) {
     return <FlightListSkeleton count={skeletonCount} />;
   }
@@ -44,14 +62,25 @@ export const FlightList: FC<FlightListProps> = ({
   return (
     <div className="flight-list">
       {flights.map((flight) => (
-        <FlightCard
+        <div
           key={flight.id}
-          flight={flight}
-          expandable={Boolean(onFlightClick)}
-          {...(onFlightClick
-            ? { onViewDetails: () => onFlightClick(flight) }
-            : {})}
-        />
+          ref={(el) => {
+            if (el) {
+              cardRefs.current.set(flight.id, el);
+            } else {
+              cardRefs.current.delete(flight.id);
+            }
+          }}
+        >
+          <FlightCard
+            flight={flight}
+            expandable={Boolean(onFlightClick)}
+            initialExpanded={flight.id === initialCurrentFlightId}
+            {...(onFlightClick
+              ? { onViewDetails: () => onFlightClick(flight) }
+              : {})}
+          />
+        </div>
       ))}
     </div>
   );