feat(project) : add delete button for empty projects with confirmation modal

Adds taskCount virtual field on Project entity, delete button in ProjectDrawer
(visible only when taskCount === 0), and a reusable ConfirmDeleteProjectModal.

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

src/Entity/Project.php

@@ -13,6 +13,8 @@ use ApiPlatform\Metadata\GetCollection;
 use ApiPlatform\Metadata\Patch;
 use ApiPlatform\Metadata\Post;
 use App\Repository\ProjectRepository;
+use Doctrine\Common\Collections\ArrayCollection;
+use Doctrine\Common\Collections\Collection;
 use Doctrine\ORM\Mapping as ORM;
 use Symfony\Bridge\Doctrine\Validator\Constraints\UniqueEntity;
 use Symfony\Component\Serializer\Attribute\Groups;
@@ -87,6 +89,15 @@ class Project
     #[Groups(['project:read', 'project:write'])]
     private bool $archived = false;
 
+    /** @var Collection<int, Task> */
+    #[ORM\OneToMany(targetEntity: Task::class, mappedBy: 'project')]
+    private Collection $tasks;
+
+    public function __construct()
+    {
+        $this->tasks = new ArrayCollection();
+    }
+
     public function getId(): ?int
     {
         return $this->id;
@@ -216,4 +227,10 @@ class Project
 
         return $this;
     }
+
+    #[Groups(['project:read'])]
+    public function getTaskCount(): int
+    {
+        return $this->tasks->count();
+    }
 }