refactor: embed film data directly in batch messages

Avoid re-parsing the entire CSV file in each batch handler by including
the film data in the message payload itself.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/Message/ImportFilmsBatchMessage.php

@@ -6,9 +6,11 @@ namespace App\Message;
 
 readonly class ImportFilmsBatchMessage
 {
+    /**
+     * @param list<array{name: string, year: int, ltbxdUri: string, date: string}> $films
+     */
     public function __construct(
         public int $importId,
-        public int $offset,
-        public int $limit,
+        public array $films,
     ) {}
 }