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/Entity/TaskStatus.php

@@ -92,7 +92,7 @@ class TaskStatus
         return $this;
     }
 
-    public function isFinal(): bool
+    public function getIsFinal(): bool
     {
         return $this->isFinal;
     }