Mobile navbar overflows

**Describe the bug**
On smaller screen sizes, the user can swipe to the right and see the menu that slides in. This behavior is not intended.

**To Reproduce**
Steps to reproduce the behavior:
1. Go to the website
2. Open devtools
3. Open responsive mode and shrink down to a viewport that is 1000px or less
4. Swipe/scroll right

**Expected behavior**
The menu should be hidden until the user clicks the hamburger icon, at which point it slides in from the right.

**Additional context**
It seems like `overflow: hidden` should be the fix here, but I have applied it to the root HTML element without success.

Start by reproducing the issue in responsive mode at a viewport of 1000px or less, then inspect the mobile navbar and its surrounding layout styles. Done means the menu cannot be reached by swiping or scrolling right while closed, but still slides in after the hamburger icon is clicked.

Rédigé par le modèle d'indexation à partir du texte de l'issue.