Shade disabled payout methods when admin turns them off

- payout_methods list now includes admin_enabled flag via JOIN on admin_payout_settings
- Disabled methods appear at 45% opacity with UNAVAILABLE/DISABLED BY ADMIN badge
  in both the cashout radio list and profile payout tab; radio is disabled so they
  can't be selected, but the delete button remains
- Set Default button hidden on disabled methods
- cashout.php server-side guard rejects submissions using a disabled method type

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

api/payout_methods.php

@@ -14,7 +14,14 @@ switch ($action) {
 
     case 'list':
         $uid = $isAdmin ? (int)($_GET['user_id'] ?? $userId) : $userId;
-        $rows = db()->prepare("SELECT * FROM payout_methods WHERE user_id=? ORDER BY is_default DESC, id ASC");
+        $rows = db()->prepare("
+            SELECT pm.*,
+                   COALESCE(aps.is_enabled, 0) AS admin_enabled
+            FROM payout_methods pm
+            LEFT JOIN admin_payout_settings aps ON aps.method_key = pm.method_type
+            WHERE pm.user_id = ?
+            ORDER BY pm.is_default DESC, pm.id ASC
+        ");
         $rows->execute([$uid]);
         echo json_encode(['success'=>true, 'methods'=>$rows->fetchAll()]);
         break;