Fix proration settings never saving or taking effect

Two bugs:
1. save() wrote bare key "allow_proration" but ProrationService reads
   dotted "enrollment.allow_proration" — now always writes "{group}.{key}"
2. loadAllSettings() tried to read bare keys but DB had dotted keys from
   seeder — now strips group prefix on read so UI always sees bare keys

Result: toggle saves correctly, ProrationService reads the live value,
mid-month enrollment now shows prorated fee (e.g. day 16 = 15/30 × fee).
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

app/Livewire/Admin/SystemSettings.php

@@ -201,7 +201,11 @@ public function loadAllSettings(): void
         $records = SystemSetting::withoutGlobalScope('academy')
             ->where('academy_id', $academyId)
             ->get()
-            ->mapWithKeys(fn ($s) => [$s->key => $s->value])
+            ->mapWithKeys(function ($s) {
+                // Strip group prefix so UI can use bare keys (e.g. "enrollment.allow_proration" → "allow_proration")
+                $bareKey = str_contains($s->key, '.') ? substr($s->key, strpos($s->key, '.') + 1) : $s->key;
+                return [$bareKey => $s->value];
+            })
             ->toArray();
 
         // Merge defaults with stored values
@@ -227,7 +231,8 @@ public function save(SettingsService $service): void
                 default => 'string',
             };
 
-            $service->set($key, $value, $group, $type);
+            // Always store as dotted key so services can read "group.key"
+            $service->set("{$group}.{$key}", $value, $group, $type);
         }
 
         session()->flash('success', __('تم حفظ الإعدادات بنجاح'));