[backend] Implement updateMarketStatus() service

[Ehonrie]

Implement updateMarketStatus() in backend/src/services/market.service.ts.

What to implement:

• db.market.update() with where: { id: market_id }
• Update status and optionally outcome
• Set resolvedAt = new Date() when transitioning to Resolved

Acceptance Criteria:

• Status updated correctly for all MarketStatus values
• resolvedAt set when status becomes Resolved
• outcome stored when provided
• Integration test covers all status transitions

[chisomvictorcv-sketch]

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

Good day I am a full stack developer with over 6 years of experience and I have good practical knowledge on this kindly assign this to me.

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

[starkiVector-090]

@starkiVector-090 has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

Hi team, I would love to work on this issue

ℹ️ Repo Maintainers: To accept this application, review their application or assign @starkiVector-090 to this issue.

[drips-wave]

Congratulations, @starkiVector-090! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on June 30, 2026.

🧑‍💻 @starkiVector-090: 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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