feat: public check-in flow and attendance (Fasa 5)

- AttendanceService: staffCheckin and walkInRegister methods
- CheckinController: QR-based check-in (staff & walk-in external)
- AttendanceCheckController: semak kehadiran & sijil status
- Views: checkin show/success/already/unavailable, semak show/result

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

resources/views/public/checkin/already.blade.php

@@ -0,0 +1,31 @@
+@extends('layouts.public')
+
+@section('title', 'Sudah Check-In')
+
+@section('hero')
+<h4 class="mb-1">{{ $program->title }}</h4>
+<div class="opacity-75 small"><i class="bi bi-calendar3 me-1"></i>{{ $program->start_date->format('d M Y') }}</div>
+@endsection
+
+@section('content')
+<div class="checkin-card card p-4 text-center">
+    <div class="mb-3">
+        <div class="rounded-circle bg-warning bg-opacity-10 d-inline-flex align-items-center justify-content-center mb-3"
+             style="width:80px; height:80px;">
+            <i class="bi bi-exclamation-circle-fill text-warning" style="font-size:2.5rem;"></i>
+        </div>
+        <h5 class="fw-bold text-warning mb-1">Sudah Check-In</h5>
+        <p class="text-muted mb-0">Kehadiran anda sudah direkodkan sebelum ini.</p>
+    </div>
+    <div class="bg-light rounded p-3 text-start">
+        <div class="row g-2">
+            <div class="col-5 text-muted small">Nama</div>
+            <div class="col-7 fw-medium small">{{ $participant->name }}</div>
+            <div class="col-5 text-muted small">Masa Check-In</div>
+            <div class="col-7 small">{{ $attendance->checked_in_at->format('d M Y, H:i') }}</div>
+            <div class="col-5 text-muted small">Sesi</div>
+            <div class="col-7 small"><span class="badge bg-primary">{{ Str::ucfirst($attendance->attendance_session) }}</span></div>
+        </div>
+    </div>
+</div>
+@endsection