Flow wallet, packs, and holds (3.11.0)

Shipped in 3.11.0. Metered usage now runs through a Flow wallet: you top it up with packs, and usage draws it down, with a hold placed when work is about to consume balance.

What is new:

• Wallet balance and history under Settings, Billing.
• Packs you buy ahead rather than overage you discover afterwards.
• Holds, so a large job cannot start and then run out halfway.
• Low balance alerts before the wallet empties, added in 3.12.1.

How this sits next to your subscription: the plan covers the product, the wallet covers metered usage on top. They are billed separately and a wallet top-up is not a subscription change.

The reason for holds rather than post-hoc billing is honesty about what will happen. A broadcast that stops at contact four thousand of ten thousand because the balance ran out is a worse outcome than one that refuses to start, and much harder to explain to whoever asked for it.