Simplify mobile test architecture and stabilize data setup

.env.example

@@ -1,11 +1,4 @@
 DB_URL=jdbc:postgresql://<host>:<port>/<db>
 DB_USER=<db_user>
 DB_PASSWORD=<db_password>
-
-WISHLISTS_USERNAME=<login_1>
-WISHLISTS_PASSWORD=<password_1>
-GIFTS_USERNAME=<login_2>
-GIFTS_PASSWORD=<password_2>
-RESERVATION_USERNAME=<login_3>
-RESERVATION_PASSWORD=<password_3>
-RESERVATION_OWNER=<login_owner>
+MOBILE_HOST=127.0.0.1