fix(migration): make Phase_100_002 idempotent to handle pre-existing columns

The medical_grace_deadline column already exists in the live DB from a
prior partial run. Converted to a closure-based migration that checks
information_schema before altering.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

database/migrations/Phase_100_002_add_medical_grace_period.php

 <?php
 declare(strict_types=1);
 
-return [
-    'up' => "
-        ALTER TABLE sa_group_players ADD COLUMN medical_grace_deadline DATE NULL DEFAULT NULL COMMENT 'Deadline for submitting medical cert' AFTER status;
-        INSERT INTO system_config (config_key, config_value, config_group, label_ar, field_type, created_at, updated_at)
-        VALUES ('sa.medical_grace_days', '14', 'sports_activity', 'مهلة تقديم الشهادة الطبية (بالأيام)', 'number', NOW(), NOW())
-        ON DUPLICATE KEY UPDATE config_key = config_key;
-    ",
-    'down' => "
-        ALTER TABLE sa_group_players DROP COLUMN medical_grace_deadline;
-        DELETE FROM system_config WHERE config_key = 'sa.medical_grace_days';
-    ",
-];
+return function (\App\Core\Database $db): void {
+    $exists = $db->selectOne(
+        "SELECT 1 FROM information_schema.columns WHERE table_schema = DATABASE() AND table_name = 'sa_group_players' AND column_name = 'medical_grace_deadline'"
+    );
+    if (!$exists) {
+        $db->raw("ALTER TABLE sa_group_players ADD COLUMN medical_grace_deadline DATE NULL DEFAULT NULL COMMENT 'Deadline for submitting medical cert' AFTER status");
+    }
+
+    $configExists = $db->selectOne("SELECT 1 FROM system_config WHERE config_key = 'sa.medical_grace_days'");
+    if (!$configExists) {
+        $db->raw("INSERT INTO system_config (config_key, config_value, config_group, label_ar, field_type, created_at, updated_at) VALUES ('sa.medical_grace_days', '14', 'sports_activity', 'مهلة تقديم الشهادة الطبية (بالأيام)', 'number', NOW(), NOW())");
+    }
+};