fix(market): keep account menu above modal content

[bobleer]

Summary

• render the shared market account menu in the global appearance overlay host so modal content cannot clip or paint over it
• anchor the menu to the account trigger with viewport collision handling, vertical flipping, and responsive width/height constraints
• preserve outside-click, Escape, focus restoration, and logout behavior across the portal boundary

Verification

• pnpm --dir src/web-ui run test:run src/features/market-account/MarketAccountControls.test.tsx src/shared/utils/fixedPopoverViewport.test.ts
• pnpm run type-check:web
• pnpm run lint:web
• pnpm run appearance:contract-audit
• pnpm run build:web