only show non-placed boats in boathouse list

src/tera/board/boathouse.rs

@@ -25,7 +25,14 @@ async fn index(
     }
 
     let boats = Boat::all_for_boatshouse(db).await;
-    context.insert("boats", &boats);
+    let mut final_boats = Vec::new();
+    for boat in boats {
+        if boat.boat.boathouse(db).await.is_none() {
+            final_boats.push(boat);
+        }
+    }
+
+    context.insert("boats", &final_boats);
 
     let boathouse = Boathouse::get(db).await;
     context.insert("boathouse", &boathouse);