"Apply now" button on front page when the registrations have closed

## 🐛 Bug Report

### What went wrong? 🤔

"Apply now" button visible on front page even when the event has already begun and registrations have closed.

### Solution

The button could be "View event" or something similar, before it changes to "View projects".

Start at the front-page event button logic and reproduce the state where the event has begun and registrations are closed. Trace the existing label transitions, then verify that the button shows an appropriate event-view action before changing to “View projects.”

索引モデルが issue の本文から書いたものです。