Implement banking system features and enhancements

- Added banking mode with checking, savings, and charity accounts, including auto-split options for income.
- Introduced banking transaction management, including transfers and charity outflows.
- Updated family settings to allow configuration of banking features and interest rates.
- Enhanced data export functionality to include bank transactions.
- Improved user interface to display banking information and donation goals.
- Updated documentation to reflect new banking features and settings.

export.php

@@ -17,7 +17,7 @@ if (isset($_GET['type'])) {
     $type = sanitizeInput($_GET['type']);
     if (in_array($type, [
         'chores', 'groceries', 'meals', 'meal_plans', 'expenses',
-        'stores', 'grocery_lists', 'grocery_catalog',
+        'stores', 'grocery_lists', 'grocery_catalog', 'bank_transactions',
     ], true)) {
         if (exportData($type)) {
             echo json_encode(['success' => true, 'message' => 'Export successful']);