Add unit tests for TransactionsController

[RedheadedProgrammer]

Closes #283

Description

Added comprehensive unit test coverage for the TransactionsController endpoints to meet testing standards.

Changes

• Created �pps/api/src/transactions/transactions.controller.spec.ts
• 13 test cases covering all controller endpoints:
  • POST /transactions: registers transactions with all network types (STELLAR, BTC, ETH)
  • GET /transactions: returns paginated list with different statuses and networks
  • GET /transactions/:id: returns single transaction, handles filtering by type/status/date, returns 404 when not found
• Follows existing test patterns in the codebase (mocked services, Jest setup)
• All tests passing locally

Testing

Ran \pnpm --filter api test\ and verified:

• TransactionsController suite: 13 passed
• No failures or warnings
• Tests properly mock TransactionsService for isolated unit testing

Type of change

• New feature (adds unit test coverage)
• This change requires a documentation update (test file documents endpoint behavior)

[vercel]

Someone is attempting to deploy a commit to the missblue00's projects Team on Vercel.

A member of the Team first needs to authorize it.

[drips-wave]

@RedheadedProgrammer Great news! 🎉 Based on an automated assessment of this PR, the linked Wave issue(s) no longer count against your application limits.

You can now already apply to more issues while waiting for a review of this PR. Keep up the great work! 🚀

Learn more about application limits