Implement the Network Fees endpoint with caching

[AlAfiz]

Description

The frontend relies on the backend to estimate transaction fees accurately. Querying Horizon directly from the frontend exposes API keys and rate limits. The backend should proxy and cache this.

Acceptance Criteria

• Implement GET /api/v1/network/fees in a NetworkController.
• Query the Stellar Horizon /fee_stats endpoint via the StellarService.
• Parse the response to return simplified baseFee and priorityFee metrics.
• Implement an in-memory cache (@nestjs/cache-manager) to store this result for 30 seconds, so 1,000 active users only trigger 2 backend requests per minute.

Technical Details

• Return the exact structure documented in the README: { success: true, data: { baseFee, priorityFee, estimatedTotal } }.

[Husten150]

@Husten150 has applied to work on this issue as part of the Stellar Wave Program's 4th wave.

i would like to work on these

ℹ️ Repo Maintainers: To accept this application, review their application or assign @Husten150 to this issue.

[drips-wave]

Congratulations, @Husten150! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on April 29, 2026.

🧑‍💻 @Husten150: 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

When opening a PR, please link it to this issue to ensure it gets tracked accurately. Points are awarded when this issue is marked as completed by the maintainer.

🤠 Repo maintainers: Please keep an eye on the contributor's progress and review their work before the due date. You can manage this issue, including adjusting its complexity and points, here.

🌊 Happy Wave 🌊