Add env-based API URL and contract IDs

[joelpeace48-cell]

Read API base URL and (optional) rewards/campaign contract IDs from VITE_* env and use them in fetch and Soroban calls. Document in frontend README.

[devxsameer]

@devxsameer has applied to work on this issue as part of the Stellar Wave Program's 3rd wave.

I’d like to take this issue. I’m a backend-leaning full stack developer with experience managing environment-based configuration, and I can integrate VITE env variables for API URLs and contract IDs, update usage across the app, and document everything clearly in the frontend README.

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

[D2758695161]

Crab Bounty Claim

Submitted PR #134 for this issue. Payment address: 0xaae0101ac77a2e4e0ea826eb4d309374f029b0a6

[Agbasimere]

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

Can I please work on this?

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

[leojay-net]

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

I would like to work on this issue.

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

[drips-wave]

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

🧑‍💻 @leojay-net: 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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