refactor(users): login and registration use JdbcTemplate for users

readme.md

@@ -131,6 +131,9 @@ layers:
 | Domain | `model`, `service`, `exception` | Plain Java models and business logic. Uses repositories, never API classes, entities or `EntityMapper`. |
 | Persistence | `persistence`, `repo` | JPA entities, Spring Data repositories, `EntityMapper`; `repo` holds `JdbcTemplate` queries. Entities never reach the API layer. |
 
+`user` owns the tables `users` and `user_settings` through the one JPA entity `UserEntity`. `login` and
+`registration` read and write `users` with `JdbcTemplate` (refresh tokens stay JPA). Every query for "a user who
+may log in and is shown to others" uses `shared/account/ActiveUser`.
 `profile` and `stats` only read data. They have no entities and use `JdbcTemplate` queries in a `repo` package.
 `version` has only an `api` package: `GET /api/version` answers the commit and build time of the running image.
 `account` (delete and nightly cleanup) sets the flag with `JdbcTemplate` in a `repo` package too, and calls Core