Feat/staff module

[Ibinola]

Description

Adds a standalone Staff module to handle internal staff management.

Key Features

• Creates the Staff entity with fields for name, email, employeeId, and role.
• Implements an enum for StaffRole (admin, manager, cleaner, etc.).
• Adds shiftStartTime and shiftEndTime fields.
• Provides full CRUD (Create, Read, Update, Delete) endpoints at /staff.

Closes #386

[vercel]

@Ibinola is attempting to deploy a commit to the naijabuz's projects Team on Vercel.

A member of the Team first needs to authorize it.

[yusuftomilola]

Approved