HRMS FACE ATTENDANCE - FINAL TWO-WAY SYNC

SERVER
1. Copy api/face_attendance into the same HRMS installation.
2. The API auto-creates the mobile/attendance support tables when first used. sql/face_attendance_mobile.sql is also included for manual installation.
3. Flutter uses the existing active admin_users credentials.
4. Branch access follows the HRMS account permissions.

ATTENDANCE
- Four slots: MORNING_IN -> MORNING_OUT -> LUNCH_IN -> FINAL_OUT.
- Working time = (Morning Out - Morning In) + (Final Out - Lunch In).
- >= 8:00 = 1.0 Present day.
- >= 4:00 and < 8:00 = 0.5 Half Day.
- < 4:00 = 0 payable/absent day.
- Monthly payable = gross salary / working days * payable present-day units.
- September 2026 uses Monday-Saturday working days (26).
- Face/mobile timestamps are authoritative in Attendance Reports; attendance_daily remains the web mirror/fallback.

TWO-WAY SYNC
- Phone -> server: pending face/attendance events are pushed whenever a sync succeeds.
- Server -> phone: sync_state.php returns current employees/faces and web/mobile attendance slot events.
- The phone reconciles server events into its local SQLite attendance state.
- Initial sync happens after login/startup.
- Automatic sync runs every 10 minutes while the app is running.
- Manual Sync button is available on the home screen.
- When the server is offline, attendance/face events remain in SQLite and are retried later.
- When the server comes back, pending local events upload first, then the latest server state is pulled.
- If attendance is changed on the web, the phone receives it on the next successful sync.

IMPORTANT
- The Flutter app is an offline-capable attendance terminal; it does not require the HRMS server to be available at the exact moment of capture.
- True background syncing after Android force-stop is not guaranteed by this source; keep the attendance app running for the 10-minute automatic polling requirement.