feat : add archive/unarchive to TaskGroupDrawer and fix isFinal serialization

Fix TaskStatus getter naming (isFinal -> getIsFinal) so Symfony serializer
properly exposes the isFinal field. Add archive/unarchive buttons and
non-final tasks info message to TaskGroupDrawer. Remove obsolete TaskType
entity and repository.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/Repository/TaskTypeRepository.php

@@ -1,17 +0,0 @@
-<?php
-
-declare(strict_types=1);
-
-namespace App\Repository;
-
-use App\Entity\TaskType;
-use Doctrine\Bundle\DoctrineBundle\Repository\ServiceEntityRepository;
-use Doctrine\Persistence\ManagerRegistry;
-
-class TaskTypeRepository extends ServiceEntityRepository
-{
-    public function __construct(ManagerRegistry $registry)
-    {
-        parent::__construct($registry, TaskType::class);
-    }
-}