Add transaction feedback system with success toasts and trade panel error boundary

[Chucks1093]

Summary

The trade flow currently gives the user no visible feedback after a confirmed transaction and crashes the full page on unexpected render errors inside the panel. Both gaps should be addressed together since they are two sides of the same trade panel reliability story.

Scope

• Add a success toast after buy confirmation: Bought {n} key{s} from {creator}
• Add a success toast after sell confirmation: Sold {n} key{s} from {creator}
• Toasts auto-dismiss after 4 seconds; error toasts are out of scope for this issue
• Wrap the trade panel in a React error boundary; fallback UI shows an inline error message and a retry button that resets the boundary
• The rest of the page (header, creator info, holdings) must remain mounted when the panel errors

Acceptance Criteria

• Success toast appears after buy confirmation with correct content
• Success toast appears after sell confirmation with correct content
• Toast auto-dismisses after 4 seconds
• Error boundary catches render errors inside the trade panel
• Retry button resets the boundary and remounts the panel
• Page outside the panel stays mounted on panel error

ETA: 12 hours

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Coordinate on Telegram

[Tijesunimi004]

I'd like to work on this issue as I'm gaining familiarity with this project

[wendypetersondev]

Hi maintainer i would like to work on this issue

[Alaka-ibr]

Hi maintainer, will appreciate you letting me work on this.

[grantfox-oss]

🦊 GrantFox — @Alaka-ibr has been assigned to this issue as part of the Official Campaign | FWC26 campaign!

Next steps:

1. Open a Pull Request referencing this issue (e.g., Closes #546)
2. Your PR will be reviewed by the accesslayerorg maintainers

Good luck! Track your progress on GrantFox.

[grantfox-oss]

🎉 This issue has been marked as completed on GrantFox as part of the Official Campaign | FWC26 campaign!

@Alaka-ibr's PR #739 was approved and merged by @Chucks1093.

🏆 @Alaka-ibr: You earned 35 FoxPoints for this contribution! Your current tier: Explorer (379 total points). Track your full progress on GrantFox.

👏 Great work, @Alaka-ibr! Keep contributing to accesslayerorg.