Optional end times and a minimum-players setting for Planner events

Not sure how long a session will run? You can now leave the end time blank when scheduling a Planner event — it'll just show the start time until you know more. There are also quick +1h/+2h/+3h/+4h buttons that fill in an end time relative to your start time, so you don't have to do the math yourself. You can also set a minimum number of participants for a session, separate from the existing maximum. It shows up right next to the sign-up count (e.g. "3/6 confirmed, min 4 needed") so everyone can see at a glance whether a session actually has enough people yet.