## ADDED Requirements

### Requirement: Live flash-sale page
The mall SHALL render active flash-sale sessions and activity products from the shared API client, including authoritative activity price, remaining stock, and sell-through. It SHALL replace `SECKILL_SESSIONS` and derived fixed product data. Shoppers SHALL purchase through the existing cart and checkout; payment and order-detail views SHALL show the snapshotted activity unit price from the order payload. This change SHALL NOT add flash-sale prices, badges, or claim CTAs to the catalog product-detail page (`/goods/[id]`); that page keeps catalog SKU pricing.

#### Scenario: choose live session
- **WHEN** a shopper selects an active flash-sale session
- **THEN** its live eligible products and countdown render without direct fixture imports

#### Scenario: order shows flash snapshot
- **WHEN** checkout applies a flash-sale price
- **THEN** payment and order-detail views show that unit price from the order payload

#### Scenario: product detail stays on catalog price
- **WHEN** a shopper opens a catalog product that is also in an active flash-sale session
- **THEN** the product-detail page still shows catalog SKU prices and does not require a flash-sale overlay in this change