Deduplicate wallet and sandbox modules

[dotunv]

Description

The wallet/ and sandbox/ modules share nearly identical logic:

• generateKeypair
• fundFromFriendbot
• Payment sending functions

Both are used by different frontend pages but implement the same core operations.

Directories:

• apps/api/src/modules/wallet/
• apps/api/src/modules/sandbox/

Proposed Approach

Option A: Merge into a single wallet module and have the Sandbox page call wallet endpoints.

Option B: Keep separate modules but extract shared logic into a common service.

Benefits

• Reduced code duplication
• Easier maintenance
• Single source of truth for wallet operations

Acceptance Criteria

• No duplicated logic between modules
• Both frontend pages (Sandbox and Wallet) continue to work
• All existing functionality is preserved
• Tests cover the deduplicated code

[Okorie2000-code]

Hi Maintainer, I'd love to work on this issue. I understand the requirements and will submit a clean, well-tested PR within 24hrs. Please assign it to me

[Abuh-Bakar]

I have required experience to complete the project and can submit PR wthin 2 days. Please consider my application.

[Babigdk]

Hi @dotunv, I'd like to work on this issue.

I have experience refactoring NestJS/TypeScript applications to eliminate duplication while preserving existing behavior. My approach will be to identify the shared wallet operations, extract them into a common service to maintain a single source of truth, and keep both the Wallet and Sandbox modules working without breaking their public APIs. I'll also add/update tests to cover the shared implementation and verify there are no regressions before submitting a clean PR.