T412315: Add Advanced Admin Features

[Abdul-Muhsin39]

Completed Task T412315.

Features Implemented:

• Bulk User Management: Added CSV upload functionality to create multiple users at once.
• System Settings: Created a configuration interface for site-wide settings (stored in DB).
• Audit Logging: Implemented middleware to track and log user actions (POST/PUT/DELETE).

Technical Notes:

• Fixed missing exports in src/lib/api.ts.
• Note: There is a merge conflict due to changes in the API file, but the code is complete and functional locally.