feat: prevent booking flow without available rooms

src/Exception/NoRoomsAvailableException.php

@@ -0,0 +1,27 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Exception;
+
+use Symfony\Component\HttpKernel\Exception\HttpException;
+
+/**
+ * Exception thrown when attempting to create a booking but no rooms are available.
+ *
+ * This exception is used to prevent users from entering the booking flow
+ * when there are no available rooms for the selected travel dates.
+ */
+class NoRoomsAvailableException extends HttpException
+{
+    public function __construct(int $dateId, int $hotelId, ?\Throwable $previous = null)
+    {
+        $message = sprintf(
+            'Leider sind für diese Reise aktuell keine Zimmer verfügbar (Travel ID: %d, Hotel ID: %d)',
+            $dateId,
+            $hotelId
+        );
+
+        parent::__construct(400, $message, $previous);
+    }
+}