feat : MCP server infrastructure setup

Install symfony/mcp-bundle, add STDIO + HTTP transport config,
API token auth on User entity with custom authenticator and firewall,
generate-api-token console command, Nginx /_mcp location, fixture token.

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

src/DataFixtures/AppFixtures.php

@@ -33,6 +33,7 @@ class AppFixtures extends Fixture
         $admin->setUsername('admin');
         $admin->setRoles(['ROLE_ADMIN']);
         $admin->setPassword($this->passwordHasher->hashPassword($admin, 'admin'));
+        $admin->setApiToken('dev-mcp-token-for-testing-only-do-not-use-in-production');
         $manager->persist($admin);
 
         // Clients