Selling rules

The plans and prices are plans; the ids are src/constants/plans.ts.

• Only the host pays. A guest never needs anything to join.
• No ads, on any plan. There is no ad SDK and no analytics in this project.
• 1.x promised "No subscription. Ever." That line is gone and must not come back in copy.
• What holds is narrower: the game on one phone is never a subscription, and nothing is sold with a countdown, a strikethrough price, a weekly plan or a delayed close button.