Fix ObjectBox Connection upsert keying off DB ID not Fediverse ID

lib/data/objectbox/objectbox_connections_repo.dart

@@ -94,7 +94,10 @@ class ObjectBoxConnectionsRepo implements IConnectionsRepo {
   @override
   bool upsertConnection(Connection connection) {
     memCache.upsertConnection(connection);
-    box.put(connection);
+    getById(connection.id).match(
+      onSuccess: (existing) => box.put(connection.copy(obId: existing.obId)),
+      onError: (_) => box.put(connection),
+    );
     return true;
   }