[BE-01] Fix buildDataKey() returning bare 'doc_' prefix — breaks all Stellar anchoring

[mftee]

Overview

buildDataKey() in StellarService constructs the Stellar manageData key by sanitizing and slicing the hash, but the return statement is incomplete — it returns the literal string "doc_" without appending the sanitized hash. This means every document gets anchored under the same Stellar data key, causing all but the first anchor to silently overwrite previous records on the ledger.

Background

File: backend/src/stellar/stellar.service.ts

The method should return "doc_" + sanitized.slice(0, 58) but currently only returns the prefix. Both anchorHash() and verifyHash() call buildDataKey(), so the entire Stellar integration is broken until this is fixed.

Acceptance Criteria

• Return statement in buildDataKey() correctly concatenates "doc_" with the first 58 characters of the sanitized hash
• Two documents with different hashes produce two different Stellar data keys
• Existing anchorHash() and verifyHash() calls work correctly end-to-end with the fix applied

[midenotch]

@midenotch has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

I'd be glad to handle this issue. I'll keep the implementation concise, maintainable, and well-documented.

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

[Maryermarh]

@Maryermarh has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

Hi, I'd like to work on this issue.

I am a fullstack developer. I am very efficient and have great attention to details. Can I please be assigned this?
ETA is 13hrs

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

[grantfox-oss]

🦊 GrantFox — @Maryermarh has been assigned to this issue!

Next steps:

1. Open a Pull Request referencing this issue (e.g., Closes #726)
2. Your PR will be reviewed by the CodeGirlsInc maintainers

Good luck! Track your progress on GrantFox.

[drips-wave]

Congratulations, @Maryermarh! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on June 30, 2026.

🧑‍💻 @Maryermarh: 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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[grantfox-oss]

🎉 This issue has been marked as completed on GrantFox!

@Maryermarh's PR #888 was approved and merged by @mftee.

🏆 @Maryermarh: You earned 35 FoxPoints for this contribution! Your current tier: Explorer (331 total points). Track your full progress on GrantFox.

👏 Great work, @Maryermarh! Keep contributing to CodeGirlsInc.