Add support for fractional kWh certificate minting

[AnnabelJoe]

Description

The current system mints whole-number kWh tokens. Meters may report fractional kWh values (e.g., 12.5 kWh). Fractional minting should be supported.

Acceptance Criteria

• energy_token supports decimal precision (e.g., 3 decimal places)
• API accepts fractional kwh values
• UI displays fractional values correctly
• Existing whole-number certificates unaffected
• SEP-41 decimals field set appropriately

Priority

Medium

Estimated Effort

Medium

Dependencies

SEP-41 compliance

Labels

enhancement, product, smart-contract

[Mistersmile4585]

@Mistersmile4585 has applied to work on this issue as part of the Stellar Wave Program's 5th wave.

Hi maintainer, I will love to work on this issue, I have extensive experience and proven knowledge building APIs and frontend, thanks i will love to hear from you.

ℹ️ Repo Maintainers: To accept this application, review their application or assign @Mistersmile4585 to this issue.

[Dev-Odun-oss]

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

I'd like to work on this issue. I've read through the codebase and I have a clear picture of what needs to be done here. I'll keep the implementation minimal and aligned with the existing patterns in the project.

ℹ️ Repo Maintainers: To accept this application, review their application or assign @Dev-Odun-oss to this issue.

[drips-wave]

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

🧑‍💻 @Dev-Odun-oss: 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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