system-locked violation types (alpha & terlambat) + proporsional poin alpha per jam

- Migration: add is_system column to violation_types, mark alpha & terlambat
- DestroyType guard: system types cannot be deleted
- UpdateType guard: slug tetap walau nama diubah untuk system types
- UI: delete button hidden, badge lock untuk system types
- Seeder: ViolationTypeDefaultsSeeder untuk fresh deploy
- AttendanceController: lookup by slug (alpha/terlambat) instead of fuzzy match
- Alpha auto-violation: poin proporsional per jam (round((points/10)*count), min 1)
- Terlambat auto-violation: poin fix sesuai jenis (2 poin)
- Also handles both A (alpha) and T (terlambat) statuses for auto-violations

app/Models/Attendance.php

@@ -0,0 +1,32 @@
+<?php
+
+namespace App\Models;
+
+use Illuminate\Database\Eloquent\Model;
+use Illuminate\Database\Eloquent\Relations\BelongsTo;
+
+class Attendance extends Model
+{
+    protected $fillable = [
+        'student_id', 'date', 'lesson_hour',
+        'status', 'notes', 'recorded_by',
+    ];
+
+    protected function casts(): array
+    {
+        return [
+            'date' => 'date',
+            'lesson_hour' => 'integer',
+        ];
+    }
+
+    public function student(): BelongsTo
+    {
+        return $this->belongsTo(Student::class);
+    }
+
+    public function recorder(): BelongsTo
+    {
+        return $this->belongsTo(User::class, 'recorded_by');
+    }
+}