Feature/pagination refactor

[MandarK07]

Pull Request

Discussion: N/A

Description

This PR refactors the paginated response models to use a single Generic type, eliminating code duplication between users and items.
Previously, models.py defined separate models for each entity list:

• UsersPublic(SQLModel)
• ItemsPublic(SQLModel)
  This implementation replaces them with a single generic PaginatedResponse[T] model:

T = TypeVar("T")
class PaginatedResponse(SQLModel, Generic[T]):
    data: list[T]
    count: int

This ensures consistency across all current and future endpoints that require pagination (e.g., returning PaginatedResponse[UserPublic] or PaginatedResponse[ItemPublic]) and reduces boilerplate code in the models file.

## Checklist

- [ ] This PR links to a GitHub Discussion for the proposed code change.
- [ ] I added tests for the change.
- [ ] The new or updated tests fail on the main branch and pass on this PR.
- [ ] Coverage stays at 100%.
- [x] The documentation explains the change if needed.