[sdk] Add retry logic to RpcService for transient Soroban RPC failures

[Otaiki1]

Summary

sdk/src/network/rpc.service.ts makes direct calls to the Soroban RPC. Transient network failures (503, timeout) cause immediate exceptions that propagate to the UI as errors.

What to do

1. Wrap RPC calls in sdk/src/utils/retry.ts (which already exists) with:
   • Max 3 retries.
   • Exponential backoff starting at 300 ms.
   • Retry only on network errors and 5xx responses — do NOT retry 4xx (user/contract errors).
2. Add a SOROBAN_RPC_MAX_RETRIES and SOROBAN_RPC_BASE_DELAY_MS config to network.config.ts.
3. Write a test that simulates 2 transient failures followed by a success and asserts the result is returned.

Acceptance criteria

• A transient RPC failure is retried up to 3 times before propagating as an error.
• 4xx responses are not retried.

[habnark]

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

hello can i work on this issue

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

[drips-wave]

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

🧑‍💻 @habnark: 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 marked as completed by a Drips Wave moderator for @habnark as part of the Stellar Wave Program's 6th Wave 🥳

Moderator's reason: [Auto-assessed] The contributor (habnark) successfully addressed the issue requirements by defining the requested SOROBAN_RPC configuration constants and adding a specific test case in PR #883 that verifies the retry logic for transient 503 failures. Although the PR bundles multiple features and the issue remains open, the merged PR and the specific test implementation (2 failures followed by 1 success) directly satisfy the acceptance criteria.

😎 @habnark: 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.

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

ℹ️ Note: This issue was marked complete via moderation. Points were issued even though the GitHub issue remains open.