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/migrations/1784100000000-AddBookingRouteDayIndex.ts

@@ -0,0 +1,21 @@
+import { MigrationInterface, QueryRunner } from 'typeorm';
+
+/**
+ * Day-level booking pool: customers select a DAY (route + day), not a specific
+ * train. The batch engine's pool query filters bookings on
+ * (origin_yard_id, destination_yard_id, scheduled_date, status); this partial
+ * index backs that scan.
+ */
+export class AddBookingRouteDayIndex1784100000000 implements MigrationInterface {
+  public async up(queryRunner: QueryRunner): Promise<void> {
+    await queryRunner.query(`
+      CREATE INDEX IF NOT EXISTS idx_bookings_route_day
+        ON freight.bookings (origin_yard_id, destination_yard_id, scheduled_date, status)
+        WHERE deleted_at IS NULL;
+    `);
+  }
+
+  public async down(queryRunner: QueryRunner): Promise<void> {
+    await queryRunner.query(`DROP INDEX IF EXISTS freight.idx_bookings_route_day;`);
+  }
+}