style: align Postcode/Outcode models with house Fillable+casts convention

app/Models/Outcode.php

@@ -2,26 +2,25 @@
 
 namespace App\Models;
 
+use Illuminate\Database\Eloquent\Attributes\Fillable;
 use Illuminate\Database\Eloquent\Model;
 
+#[Fillable(['outcode', 'lat', 'lng'])]
 class Outcode extends Model
 {
+    public $timestamps = false;
+
     protected $primaryKey = 'outcode';
 
     public $incrementing = false;
 
-    public $timestamps = false;
-
     protected $keyType = 'string';
 
-    protected $fillable = [
-        'outcode',
-        'lat',
-        'lng',
-    ];
-
-    protected $casts = [
+    protected function casts(): array
+    {
+        return [
             'lat' => 'float',
             'lng' => 'float',
         ];
     }
+}

app/Models/Postcode.php

@@ -2,27 +2,25 @@
 
 namespace App\Models;
 
+use Illuminate\Database\Eloquent\Attributes\Fillable;
 use Illuminate\Database\Eloquent\Model;
 
+#[Fillable(['postcode', 'outcode', 'lat', 'lng'])]
 class Postcode extends Model
 {
+    public $timestamps = false;
+
     protected $primaryKey = 'postcode';
 
     public $incrementing = false;
 
-    public $timestamps = false;
-
     protected $keyType = 'string';
 
-    protected $fillable = [
-        'postcode',
-        'outcode',
-        'lat',
-        'lng',
-    ];
-
-    protected $casts = [
+    protected function casts(): array
+    {
+        return [
             'lat' => 'float',
             'lng' => 'float',
         ];
     }
+}