[server] - Add GraphQL Subscription Layer for Live Marketplace Updates

[dark-sarge]

Location: server/src/graphql/

Description

The current SSE approach covers authenticated per-user events well, but public marketplace data (new listings appearing, listings selling out) benefits from a more flexible subscription model. A GraphQL layer with subscriptions would enable the frontend to subscribe to live listing updates without polling.

Acceptance Criteria

• graphql-yoga (or Apollo Server) is added to the server and mounted at /graphql.
• A Query type exposes: trades(status, assetType, page, limit) and trade(id).
• A Subscription type exposes: tradeCreated (emits when a new listing is posted) and tradeStatusChanged(tradeId) (emits when a specific trade's status updates).
• Subscriptions use WebSocket transport (graphql-ws protocol).
• The REST API is kept intact — GraphQL is additive, not a replacement.
• The frontend marketplace page optionally subscribes to tradeCreated and appends new cards to the grid in real time without a full page refresh.

---

[faithylet]

@faithylet has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

Hi, I’d like to work on this issue.

I understand that the goal is to introduce a GraphQL subscription layer to support live, real-time updates. I’ll first review the existing GraphQL schema and event infrastructure, identify the appropriate events and subscription flow, and then implement the subscription resolvers while keeping them consistent with the project’s current architecture.

I’ll also handle subscription lifecycle and error cases properly and add tests for the key subscription behavior. I’ll aim for a focused implementation that integrates cleanly with the existing event system without introducing unnecessary changes.

I’d appreciate it if you could assign this issue to me. I’m ready to work on it and submit a focused PR.

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

[peace-cyber09]

@peace-cyber09 has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

hello
i would love to work on this

ℹ️ Repo Maintainers: To accept this application, review their application or assign @peace-cyber09 to this issue.

[drips-wave]

Congratulations, @peace-cyber09! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on August 31, 2026.

🧑‍💻 @peace-cyber09: 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 🌊

[drips-wave]

This issue has been completed by @peace-cyber09 as part of the Stellar Wave Program's 8th Wave 🥳

😎 @peace-cyber09: 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.

🧑‍💻 Repo maintainers: How'd the contributor do? Leave a review to share your experience working with them.