Add staff and student management features

Staff management:

• Use new API for staff registration (Close #46 (closed)).
• Add option to grant permanent and temporary staff designations to existing staffs (Close #47 (closed), #48 (closed)).
• Add user-specific dashboards and sidebars (Close #51 (closed), #52 (closed)).

Student management:

• Show unified student profile page for students and admins (Close #55 (closed)).
• Show guardian and employment preferences details directly in student profile.
• Clean up student profile and improve UI/UX.