Add full MIT license text and author credit (`retoor@molodetz.nl`) as file-level comments across all view files (`about.py`, `docs.py`, `index.py`, `login.py`, `login_form.py`, `logout.py`, `register.py`, `register_form.py`). Also fix `form.is_valid` to `form.is_valid()` in login views and consolidate session assignment into a single `update()` call in `login.py`.