[collector] can now collect Teile and list them

If a newly entered Teil already exists, we ignore that and do nothing.

"name" could become a primary key...

collector/urls.py

@@ -7,4 +7,6 @@ app_name = "collector"
 urlpatterns = [
     path("", views.index, name="index"),
     path("recorded/<int:teil_id>/", views.detail, name="detail"),
+    path("enter/", views.enter, name="enter"),
+    path("all/", views.list_all, name="all"),
 ]