Implement missing CredentialsService or remove unused controller

[Hallab7]

Description

CredentialsController exists but has no corresponding service implementation. Either complete the feature or remove the dead code to avoid confusion.

Either implement CredentialsService with credential retrieval, validation, and formatting logic, or remove CredentialsController if the feature is not yet planned.

Acceptance criteria

• If implementing: CredentialsService handles credential lookups, validation, and export formats
• If implementing: Controller methods work end-to-end with proper tests
• If removing: All credential-related code removed cleanly
• Decision documented in ADR or commit message
• No unused imports or dead code remains

Testing requirements

• Implementation includes unit tests for service methods
• Controller tests cover success and error cases
• npm run lint and npm run test pass
• API documentation reflects current state

Files

src/credentials/, docs/adr/

Suggested branch

feat/complete-credentials-module

Suggested commit message

feat(credentials): implement credential service