Show liquidation price lines on chart

[emptyteabot]

Summary

• Add a persisted showLiquidationsOnChart account setting.
• Draw dashed liquidation-price lines for active positions on the selected market chart.
• Recompute the lines when positions, market risk data, funding trackers, or chart visibility settings change.

Validation

• npm ci
• npm run build
• git diff --check

Closes #7

Payout address if accepted: 0xe2e86bdb8753c24032f2ad42b4c1bd9748385a7d (EVM wallet; USDC on Arbitrum/Base or USDT on BSC as applicable).

[emptyteabot]

Note for review: the Vercel status links to an account deployment block, not a build/runtime failure from this PR. I validated locally with �npm ci�, �npm run build�, and �git diff --check�.