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>

frontend/components/project/ProjectGroupTab.vue

@@ -62,6 +62,7 @@
             v-model="drawerOpen"
             :group="selectedItem"
             :project-id="projectId"
+            :tasks="[...activeTasks, ...archivedTasks]"
             @saved="onSaved"
         />
     </div>