[Frontend] Document API integration and error mapping

[floxxih]

Add docs that define frontend API wrappers and mapping from backend errors to user messages.

Acceptance Criteria:

• Endpoint groups are listed
• Error code mapping table exists
• Retry strategy is documented

[manueldezman]

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

Hello, I am a Front end developer and devrel engineer, and i have worked on a few API doucmentations, would love to work on this, If assigned.

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[Georgechisom]

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

Hi, This is my field, let me resolve this issue

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[drips-wave]

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

🧑‍💻 @Georgechisom: 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.

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[drips-wave]

This issue has been completed by @Georgechisom as part of the Stellar Wave Program's 5th Wave 🥳

😎 @Georgechisom: You earned 200 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. You can also Leave a review to share your experience working on this issue.

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