Updated the event page

Today I mainly worked on improving the event page. Some time ago I received a request from Fujisaka at NAgoya BOOK CENTER to display the event page images larger. However, making them larger made the title and description harder to see, and pushed the sign-up button toward the bottom of the screen, so I spent some time wondering what to do. On apps it's common to fix the bottom area of the screen, so I tried the same approach and it worked easily — the sign-up button is now always visible. I hope this increases event sign-ups.