fix(security) : add role checks on Gitea API resources and all MCP tools

- GiteaBranch, GiteaBranchName, GiteaPullRequest: require ROLE_USER
- All 22 MCP tools: require ROLE_USER (ROLE_ADMIN for users/clients listing)

Tickets: T-002, T-007

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

src/Mcp/Tool/Task/DeleteTaskTool.php

@@ -8,6 +8,8 @@ use App\Repository\TaskRepository;
 use Doctrine\ORM\EntityManagerInterface;
 use InvalidArgumentException;
 use Mcp\Capability\Attribute\McpTool;
+use Symfony\Bundle\SecurityBundle\Security;
+use Symfony\Component\Security\Core\Exception\AccessDeniedException;
 
 use function sprintf;
 
@@ -17,10 +19,15 @@ class DeleteTaskTool
     public function __construct(
         private readonly TaskRepository $taskRepository,
         private readonly EntityManagerInterface $entityManager,
+        private readonly Security $security,
     ) {}
 
     public function __invoke(int $id): string
     {
+        if (!$this->security->isGranted('ROLE_USER')) {
+            throw new AccessDeniedException('Access denied: ROLE_USER required.');
+        }
+
         $task = $this->taskRepository->find($id);
 
         if (null === $task) {