feat(user-center): add cash wallet balance separate from credits

Introduce AKSRT_Balance (user_meta aksrt_balance + balance_log) for
Zibll-like pay_balance wallet. User center assets panel shows wallet
and points; balance gateway/card-pass/refunds credit cash when enabled.

inc/helpers/aksrt-user-dashboard.php

@@ -81,6 +81,10 @@ function aksrt_get_user_dashboard_view(int $user_id, array $args = []): array {
         ? AKSRT_Settings::get_currency_name()
         : __('积分', 'aksrt');
 
+    // Cash wallet (Zibll pay_balance) — separate from points.
+    $balance_enabled = $is_own_profile && class_exists('AKSRT_Balance') && AKSRT_Balance::enabled();
+    $wallet_balance  = $balance_enabled ? AKSRT_Balance::balance($user_id) : 0.0;
+
     $user_home_manager = $include_governance && class_exists('AKSRT_User_Home')
         ? AKSRT_User_Home::get_instance()
         : null;
@@ -103,6 +107,8 @@ function aksrt_get_user_dashboard_view(int $user_id, array $args = []): array {
         'credit_balance'   => $credit_balance,
         'currency_name'    => $currency_name,
         'credits_enabled'  => $credits_enabled,
+        'balance_enabled'  => $balance_enabled,
+        'wallet_balance'   => $wallet_balance,
         'is_own_profile'   => $is_own_profile,
     ];
 }