Fix seed failures: name_en column is NOT NULL, use empty string

The chart_of_accounts.name_en column is VARCHAR(200) NOT NULL.
Both seeds were passing null which caused integrity constraint violations.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

database/seeds/Phase_43_001_seed_full_chart_of_accounts.php

@@ -614,7 +614,7 @@ return function (Database $db): void {
             $id = $db->insert("chart_of_accounts", [
                 "account_code" => $code,
                 "name_ar" => $nameAr,
-                "name_en" => null,
+                "name_en" => "",
                 "account_type" => $type,
                 "account_nature" => $nature,
                 "parent_id" => $parentId,

database/seeds/Phase_44_001_seed_trial_balance_2024_2025.php

@@ -42,7 +42,7 @@ return function (Database $db): void {
         return $db->insert('chart_of_accounts', [
             'account_code'    => $code,
             'name_ar'         => $nameAr,
-            'name_en'         => null,
+            'name_en'         => '',
             'account_type'    => $type,
             'account_nature'  => $nature,
             'parent_id'       => $parentId,