Add a 'Question Timer' toggle to game settings that lets the host disable
the countdown timer. When disabled, questions show ∞ instead of a countdown,
the host gets an 'End Question' button to manually advance, and all correct
answers receive maximum points.
Also fix a bug where per-question time limits were ignored — the timer and
scoring always used the hardcoded 20-second default instead of each question's
individual timeLimit.
