Board game reservation view

[ondryaso]

• Don't send a Discord message when making a reservation for other user and assigning it at the same time:
  1. Zarezervovat pro uživatele
  2. Finish the reservation using Zarezervovat a vzít si na starost or Zarezervovat a předat
  3. A message about a user making a new reservation is sent to Discord. This is, however, useless and confusing.
• Also don't send the message when a manager creates a reservation for themselves using Zarezervovat a převzít.
• Change the label of the Zarezervovat a předat button to something more understandable.
• Make the whole flow clearer: the Zarezervovat pro uživatele option is hidden in the Deskovky menu and basically just changes the games selection form's internal state without making it visible somehow. Also, it's not entirely clear that the only way to get out of this mode is to click the Zrušit tvorbu rezervace button.

When there's a game in cart, we should show a semi-transparent panel across the bottom of the page with several buttons:

• Dokončit rezervaci
• Zrušit rezervaci
• Vytvořit rezervaci pro uživatele (managers only)

then we should also get rid of the Zarezervovat pro uživatele link in the menu.