refactor(frontend): replace explicit any types in accounts service

[Brownteen18]

Description

This PR replaces explicit any usage in the accounts frontend service with concrete TypeScript interfaces for the API responses returned by the accounts service. The change is intentionally scoped to a single service file to keep the review focused and make the response contracts clearer for future development.

Related Issues

Closes #16

Type of Change

• 🧹 Refactor / chore

Checklist

• My code follows the project's style guidelines (ruff check / npm run lint)
• I have added tests that prove my fix/feature works or explained why not
  • No tests were added because this change only improves TypeScript typings and does not affect runtime behavior.
• Existing tests pass locally (pytest) (Not applicable – frontend-only change.)
• I have updated documentation where needed (Not applicable – no behavior changes.)
• I have not committed any secrets, .env files, or personal data

Screenshots (if UI change)

N/A

[Brownteen18]

Hi!
Sorry for the delay.
I've completed the requested changes and opened a PR for review. The PR focuses on replacing the explicit any usage in frontend/lib/services/accounts.ts with proper TypeScript interfaces while keeping the scope limited to a single service area.
Thanks for your time, and I look forward to your feedback!

[sanmaxdev]

Looks good to me. The response types match the backend contracts, and the frontend lint and production build pass. Thanks for keeping the change focused! 🙌