HRMS FIELD TRACKER - AUTHORIZATION TOKEN FIX

Problem fixed:
The Field Tracker app sends the mobile token in Authorization: Bearer ... and also
in X-Auth-Token/auth_token. Some Apache/PHP XAMPP configurations do not expose the
Authorization header to PHP for multipart/form-data requests, which caused:
"Missing authorization token" when Start Duty/End Duty was pressed.

Fix:
api/field_tracking/common.php now accepts the token in this order:
1) Authorization: Bearer <token>
2) X-Auth-Token: <token>
3) multipart POST field: auth_token

The Flutter app already sends X-Auth-Token and auth_token for multipart requests,
and the client copy also validates that login returned a non-empty token.

Deployment:
1. Replace your HRMS server's api/field_tracking/common.php with the fixed file.
2. Replace the Flutter project's lib/main.dart and lib/api_service.dart with the fixed files.
3. Run flutter clean, flutter pub get, then build/install the APK again.
4. Login again in the app so a fresh mobile token is stored.