Concepts docs: Token transfer flow & Stellar asset handling

[codebestia]

Write contracts/docs/concepts-token-transfer-flow.md explaining how token_transfer relates to real Stellar assets, and how the on-chain transfer flow connects to the off-chain system — specifically apps/backend/src/services/stellarListener.ts and the tokenTransfers database table that mirrors transfer state off-chain.

Acceptance criteria:

• Explains what "token" means in this contract's context (Stellar Classic asset via SAC, or a custom token) and how set_token_contract fits in
• Traces one transfer end-to-end: on-chain call → what the backend's listener observes → what gets written to the tokenTransfers table → what the frontend/user sees
• Cross-references the backend's database schema doc for the tokenTransfers table shape

[lightnoor890]

@lightnoor890 has applied to work on this issue as part of the Stellar Wave Program's 7th wave.

Kindly assign my boss

ℹ️ Repo Maintainers: To accept this application, review their application or assign @lightnoor890 to this issue.

[cythecode]

@cythecode has applied to work on this issue as part of the Stellar Wave Program's 7th wave.

Hello maintainer, i’ve got this covered! Ready to drop a high-impact, clean PR that gets this merged seamlessly

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

[mayborn005]

@mayborn005 has applied to work on this issue as part of the Stellar Wave Program's 7th wave.

Hello Maintainer, I'd like to work on this issue. I have experience with backend development and state management, and I can implement this. Please consider assigning it to me.

ℹ️ Repo Maintainers: To accept this application, review their application or assign @mayborn005 to this issue.

[drips-wave]

Congratulations, @lightnoor890! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on July 30, 2026.

🧑‍💻 @lightnoor890: 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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