Implement feature: Round clock - Stop the timer if the round ends early

[Christian-Toney]

Dependencies

• Implement feature: Round clock - Round timer on the player's screen #119: Required because the timer should be visible to the player.
• Implement feature: Distinguish the last five seconds of the round #121: Required because the round could stop during the last five seconds.

Completion criteria

Detect when the round ends and hide the timer when it does.