Web trade: market stats header

[0xMegie]

Area: apps/web/src/features/trade/components/MarketStatsHeader.tsx

Goal: Verify 24h volume, open interest, and mark/index price render from fixtures.

Tasks:

• Render with a fixed market stats fixture.
• Assert volume, open interest, and price values use shared formatters.
• Test missing/unavailable stat fallbacks.

Acceptance:

• No NaN or raw protocol-scale numbers leak to the UI.
• bun run --cwd apps/web test passes.