Schedule page fixes

[michelleyeoh]

• update margin-bottom to 8px between all event cards

app/(pages)/(hackers)/_components/HomeHacking/ScheduleSneakPeek.tsx:

• Speak Peak to your schedule: empty state
• make arrow larger on hover

app/(pages)/(hackers)/(hub)/schedule/page.tsx:

• fix May 9 and 10 toggle & fix sticky mobile may 9 and 10 visiblity: see requested mvp fixes 2.0 #386 (comment)

app/(pages)/(hackers)/_components/Schedule/CalendarItem.tsx:

• add hover states for add buttons