Allow milestones to be closed and reopened

crates/app/src/api.rs

@@ -141,6 +141,7 @@ pub async fn save_milestone(
                 title: draft.title,
                 description: draft.description,
                 due_on: draft.due_date.map(api_date),
+                state: if draft.closed { "closed" } else { "open" }.into(),
             },
         )
         .await