feat(train-scheduling): add day-level booking pool and available days query

apps/edr-freight-web/backoffice/src/hooks/trainScheduling/useTrainScheduling.ts

@@ -132,6 +132,29 @@ export const useBookableSchedules = (
     enabled: Boolean(originYardId && destinationYardId),
   });
 
+/**
+ * Day-level pool: which days have an OPEN departure on the route. Staff pick a
+ * day (not a train) when creating a booking; the engine assigns the train.
+ */
+export const useAvailableDays = (
+  originYardId?: string | null,
+  destinationYardId?: string | null,
+) =>
+  useQuery({
+    queryKey: [
+      ...QUERY_KEYS.TRAIN_SCHEDULING.ROOT,
+      "available-days",
+      originYardId ?? "",
+      destinationYardId ?? "",
+    ],
+    queryFn: () =>
+      trainSchedulingService.getAvailableDays(
+        originYardId ?? undefined,
+        destinationYardId ?? undefined,
+      ),
+    enabled: Boolean(originYardId && destinationYardId),
+  });
+
 export const useTrainTrack = (id: string | undefined) =>
   useQuery({
     queryKey: QUERY_KEYS.TRAIN_SCHEDULING.track(id ?? ""),