Add shift swap and leave request approval system to employer dashboard

[ujwalsharma07]

Summary
Added the Shift Swap / Leave Request Approval System to the Employer Dashboard in the Frontend Employer Panel.

Changes made
1. added a new Shift Swap / Leave Requests section
2. displayed shift swap and leave request items
3. added approve and reject actions for each request
4. updated request status in the UI
5. added styling for the request approval section
6. kept the existing dashboard, incident reports, and priority shifts sections working

Testing
1. ran the Employer Dashboard locally
2. verified request list displays correctly
3. verified both shift swap and leave requests are visible
4. verified approve button updates request status
5. verified reject button updates request status
6. confirmed the dashboard still loads correctly after changes

[neethuchandhavarkar]

Checkout the branch into local machine. The priority dashboard which was in this request: #279 is working here.
I would like to understand how is filtering the priority of the shift being carried out? Is it based on the date or other factors in place? I would suggest that to introduce filtering so that it gives a much cleaner look and better user experience. For shift swap, is there a better to way to introduce this instead making it below the priority dashboard?