More intuitive design for Peeks

[upsiflu]

• Visually merge P and byline; push arrow to horizontal center
• In horizontal lists,
  • split F and peek vertically (ca. 1:2)
  • center F horizontally
• Make peek 3 lines (9 units) wide/large in the dominant direction
• Prefocus upcoming if available (#17)

Time: 3 hours User story: "I'm looking for the upcoming MaT lab. As I click Lab, I see that the current Series is showing a sneak peek into the upcoming event XY, which I can click to get to the event." Severity: Low

[upsiflu]

TODO: Check how recent design updates have affected this UX issue.