fix: resolve known issues and improve code standards

- Fix known bugs in user, plan, and server modules
- Standardize code formatting and structure
- Optimize database queries and model relationships
- Improve request validation and error handling
- Update admin controllers for better consistency

app/Models/Coupon.php

@@ -14,7 +14,8 @@ class Coupon extends Model
         'created_at' => 'timestamp',
         'updated_at' => 'timestamp',
         'limit_plan_ids' => 'array',
-        'limit_period' => 'array'
+        'limit_period' => 'array',
+        'show' => 'boolean',
     ];
 
     public function getLimitPeriodAttribute($value)