Fix missing left outline on Mark as read button (#9426)
The hidden CSRF input was the first child of the form, directly before the
Mark as read button. Theme rules such as `.stick input + .btn` and
`.stick .btn:first-child` therefore treated the button as the second element
of an input + button group: no left border and no rounded left corners.
Move the input back inside the dropdown, as it was before #9205.
Fixes #9359
Changes proposed in this pull request:
- In `app/layout/nav_menu.phtml`, move the hidden `_csrf` input of the "Mark as read" form back inside the `#nav_menu_read` dropdown (where it was before #9205), instead of being the first child of the form right before the `read_all` button.
- Because of that input, many theme rules written for `input + .btn` groups (`.stick input + .btn`, and `.btn:first-child` no longer matching) removed the left border and the rounded left corners of the "Mark as read" button. This affected Alternative Dark, Origine and the themes built on them (Dark, Dark-pink, Origine-compact), Pafat, and gave a stray separator and square corners in Flat, Ansum and Mapco.
M. Önlük