Add integration test for trade panel price preview

[baedboibidex-cmyk]

Adds a buy-side total price preview to TradeDialog that shows the estimated cost for the entered quantity, and includes an integration test verifying the preview updates correctly for quantities 1 and 2, and is hidden when the input is empty or zero.

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#596	Add integration test for trade panel showing correct price preview before transaction is submitted	Link to this issue

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[github-actions]

👋 Hey @baedboibidex-cmyk, thanks for your contribution!

This PR is targeting main directly. We use main for stable releases only — all contributions should be opened against the dev branch instead.

Please close this PR and reopen it with dev as the base branch. If you're unsure how to do that, you can change the base branch using the Edit button at the top of this PR page.

Closing this PR automatically. See you in dev! 🚀