Sederhanakan ambang SP: hapus kolom max_points

- max_points tidak pernah dipakai logika penerbitan SP (trigger hanya baca
  min_points: level dgn ambang tertinggi <= total poin siswa)
- Migrasi drop kolom; model, MasterDataController, ResetController (seeder)
  dibersihkan; form Ambang SP & form tambah cukup satu angka (Min Poin)
- Dashboard Ambang SP: batas atas level dihitung dari min_points level
  berikutnya (level terakhir = tak terbatas), urutan dijamin orderBy min_points
- Test: 29 passed / 99 assertion

app/Models/SpThreshold.php

@@ -7,7 +7,7 @@ use Illuminate\Database\Eloquent\Model;
 class SpThreshold extends Model
 {
     protected $fillable = [
-        'name', 'slug', 'min_points', 'max_points',
+        'name', 'slug', 'min_points',
         'color', 'default_description', 'is_active',
     ];
 
@@ -15,7 +15,6 @@ class SpThreshold extends Model
     {
         return [
             'min_points' => 'integer',
-            'max_points' => 'integer',
             'is_active' => 'boolean',
         ];
     }