🐛(components): add missing button types and keys

Add type="button" to the EditMobility and UploadStudents buttons
to prevent default form submission behavior.
Include a key prop on Student components in Promotion for stable list rendering.

routes/(apps)/students/(_components)/Promotion.tsx

@@ -22,7 +22,7 @@ export default function Promotion(props: PromotionProps) {
         <tbody>
           {props.students
             .filter((student) => student.promotionId === props.promo.id)
-            .map((student) => <Student student={student} />)}
+            .map((student) => <Student key={student.id} student={student} />)}
         </tbody>
       </table>
     </div>