Add helper for displaying sell proceeds estimate before confirmation

[Chucks1093]

Summary
Users see the final sell proceeds only after the transaction is built, making it impossible to evaluate the trade before committing. A pre-confirmation estimate helper that computes and displays approximate proceeds gives users the information needed to decide.

Scope

• add a helper that computes an estimated sell proceeds amount from the current supply and sell quantity
• display the estimate in the sell flow before the confirmation step
• label the estimate clearly as approximate

Acceptance Criteria

• a proceeds estimate is shown before the user reaches the sell confirmation step
• the estimate is labeled as approximate
• if the estimate cannot be computed the UI shows a cannot estimate message

Contributor coordination: if you pick this up, reach out in Telegram for updates or clarification: https://t.me/accesslayerorg

[michaelvic123]

@michaelvic123 has applied to work on this issue as part of the Stellar Wave Program's 5th wave.

please assign this issue to me

ℹ️ Repo Maintainers: To accept this application, review their application or assign @michaelvic123 to this issue.

[drips-wave]

Congratulations, @victor62-art! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on June 2, 2026.

🧑‍💻 @victor62-art: Please resolve the issue such that the repo's maintainers have enough time to review your contribution before the due date. You'll earn Points for completing the issue on-time, which will make you eligible for a share of the Stellar Wave Program's reward pool.

Warning

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[drips-wave]

This issue has been marked as completed by a Drips Wave moderator for @victor62-art as part of the Stellar Wave Program's 5th Wave 🥳

Moderator's reason: [Auto-assessed] The contributor has successfully implemented the requested helper function and UI components to display sell proceeds estimates. The PR directly addresses all acceptance criteria from the issue, is merge-ready, and has received no objections from maintainers since it was opened.

😎 @victor62-art: You earned 150 Points for completing this issue! After the current Wave ends, you'll be eligible for a percentage of the Wave's reward pool based on the percentage of total points you've earned. Learn more here.

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ℹ️ Note: This issue was marked complete via moderation. Points were issued even though the GitHub issue remains open.

[grantfox-oss]

🎉 This issue has been marked as completed on GrantFox!

@victor62-art's PR #419 was approved and merged by @Chucks1093.

🏆 @victor62-art: You earned 35 FoxPoints for this contribution! Your current tier: Explorer (961 total points). Track your full progress on GrantFox.

👏 Great work, @victor62-art! Keep contributing to accesslayerorg.