Improve overlapping events: spacing and drag-and-drop UX

[tyler-dane]

Follow-up from #234 (#213). That PR focused on the baseline functionality of overlapping events. This one focuses on providing better styling and UX for these overlapping events

• Add space between overlapping events. Reference how Outlook does this.
  • This will make it easier to see and click events that overlap
• When dragging an overlapping event, the event width expands to the full column.
  • Without this, the dragged event's width doesn't match the cursor or column lines, which makes repositioning it feel awkward.
  • Reference: Outlook, Gcal, Notion Cal, Vimcal

[tyler-dane]

@that-one-arab I asked you to work on #140 , but I think it makes sense to wrap this one up beforehand. That work?

[that-one-arab]

@tyler-dane Yes that's better, on it.