feat(Volunteer):Volunteer signup and qrcode

Create a new API to determine the volunteer’s current medical camp status.

The status is based on:

Today’s camp availability

Volunteer registration status

Volunteer attendance status

The API will return a status that the frontend uses to decide the screen:

No camp scheduled screen

Camp registration page

QR code attendance screen

Volunteer dashboard

Reuse the existing signup and attendance logic.

Do not duplicate or modify existing routes or services.

when new camp schedule for volunteer

when volunteer register for camp

**when admin can mark the attendance for volunteer **

Issue #151 (closed)