make all calls to back_to_main explicit and remove unused params

I did this by copy pasting

```python
back_to_main(domain, app_id=app_id, module_id=module_id, form_id=form_id, unique_form_id=unique_form_id, edit=edit, error=error, page=page)
```
to replace every `back_to_main(**locals())` one by one, letting PyCharm highlight the variables that weren't in scope, and deleting them. This gives me high confidence that I didn't screw anything up / change the behavior at all.