let a user filter by mutiple faculties

**Is your feature request related to a problem? Please describe.**
There should be a way to select timetables with 2 faculties I like

**Describe the solution you'd like**
Use https://shadcn-multi-select-component.vercel.app/ to select multiple faculties

**Additional context**

Start by locating the existing faculty selector and timetable filtering entry points in the TypeScript application, then review the referenced shadcn multi-select component for the intended interaction. Done means users can select two or more faculties and receive timetables matching those selections without losing the existing filtering behavior.

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