Add delete button on the enemy detail page

CSRF-protected POST to /enemies/{id}/delete with a confirm. Any
combatants referencing the enemy keep their snapshotted stats (the FK
sets enemy_id null), so deleting a monster type won't disturb a fight.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/Controller/EnemyController.php

@@ -100,6 +100,20 @@ class EnemyController extends AbstractController
         return $this->handleForm($request, $em, $enemy);
     }
 
+    #[Route('/enemies/{id}/delete', name: 'app_enemies_delete', requirements: ['id' => '\d+'], methods: ['POST'])]
+    public function delete(Request $request, Enemy $enemy, EntityManagerInterface $em): Response
+    {
+        if ($this->isCsrfTokenValid('delete-enemy-'.$enemy->getId(), (string) $request->request->get('_token'))) {
+            $name = $enemy->getName();
+            // Combatants keep their snapshotted stats; enemy_id is set null by the FK.
+            $em->remove($enemy);
+            $em->flush();
+            $this->addFlash('success', sprintf('Deleted "%s".', $name));
+        }
+
+        return $this->redirectToRoute('app_enemies');
+    }
+
     private function handleForm(Request $request, EntityManagerInterface $em, Enemy $enemy): Response
     {
         $isNew = null === $enemy->getId();