feat: Ensure consistent ordering of games, users, and user opinions, and add DerefMut for User.

backend/src/main.rs

@@ -75,6 +75,8 @@ async fn add_game(
 
     games.push(game.clone());
 
+    games.sort_unstable_by(|g1, g2| g1.title.cmp(&g2.title));
+
     let users = user_list.lock().await;
     save_state(&games, &users);
 
@@ -113,6 +115,10 @@ async fn add_opinion(
             existing.would_play = req.would_play;
         } else {
             user.person.opinion.push(opinion);
+
+            user.person
+                .opinion
+                .sort_unstable_by(|o1, o2| o1.title.cmp(&o2.title));
         }
         result = Some(user.person.clone());
     }