Display the grace period state on the dashboard

**Goal.** A paid customer over their plan limit knows whether it is costing them money.

We do not charge for the first billing month an organisation goes between 100% and 200% of its limit. Every month over after that is charged as overage. That first month is the **grace period**, the name used throughout the codebase and on the page.

So an organisation sitting at 118% is in one of two situations, and the page cannot currently tell them apart:

- **covered**, nothing to pay this month
- **charged**, at the overage rate

**Where it appears**

- the over-limit banner
- the line under the meter
- the existing quota warning, which today says "automated billing for the overages may apply" because it cannot tell either

Needs #8256, which returns whether the covered month has been used.

**Done when** an organisation at 118% is told whether it is being charged, and nothing on the page hedges.