feat(train-scheduling): implement day-level booking pool

- Added `unplaced` method in `BookingNotifierService` to log warnings for bookings that cannot be placed on any train.
- Introduced `getAvailableDays` method in `TrainSchedulingService` to retrieve distinct days with open departures for a given route.
- Created `AvailableDaysQueryDto` for querying available days based on origin and destination yards.
- Updated `TrainSchedulingController` to expose an endpoint for available days.
- Modified frontend components to support day-level booking, allowing customers to select only a day without pinning to a specific train.
- Removed references to train schedules in booking forms and review steps, emphasizing day selection.
- Added a database migration to create an index for efficient querying of bookings by route and day.

apps/edr-freight-api/src/modules/train-scheduling/batch-window.util.ts

@@ -55,6 +55,16 @@ function eatParts(date: Date): EatDateParts {
   };
 }
 
+/**
+ * The EAT calendar day a timestamp falls on, as `yyyy-MM-dd`. This is the day
+ * key for day-level booking pools — it must match the day the portal calendar
+ * renders, so always derive day keys through this (never `toISOString().slice`).
+ */
+export function eatDay(date: Date): string {
+  const { year, month, day } = eatParts(date);
+  return `${year}-${String(month).padStart(2, '0')}-${String(day).padStart(2, '0')}`;
+}
+
 /** Build a UTC Date for a given EAT local wall-clock time on a calendar day. */
 function eatToUtc(
   year: number,