refactor: extract usersRouter logic into user.repository.ts and/or user.service.ts

[coderabbitai]

The usersRouter contains business logic that should be moved to a dedicated repository and/or service layer.

File: src/server/api/routers/users.ts line 88

Action required:

• Create src/server/repositories/user.repository.ts and/or src/server/services/user.service.ts.
• Move query/mutation logic out of the router and into the new files.
• Update usersRouter to delegate to the repository/service.

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Requested by @Producdevity — related to PR #375