fix(payment): wire balance wallet end-to-end when pay_balance_s is on

Opening 余额功能 alone now enables cash-wallet pay (unless 余额支付 is explicitly off). Drop points-as-balance fallback, stop fake method injection, expose real wallet in cashiers, and honor auto_to_balance on recharge fulfill.

assets/admin/src/schema/sections/payment/gateway.js

@@ -12,7 +12,7 @@ export const gatewaySchema = {
     payment_wechat_enabled: false,
     payment_alipay_enabled: false,
     payment_paypal_enabled: false,
-    payment_balance_enabled: false,
+    payment_balance_enabled: true,
     payment_card_pass_enabled: false,
     payment_xunhupay_enabled: false,
     payment_xhpay_enabled: false,
@@ -73,7 +73,7 @@ export const gatewaySchema = {
         { key: 'payment_alipay_enabled', label: '支付宝', type: 'switch', default: false },
         { key: 'payment_paypal_enabled', label: 'PayPal', type: 'switch', default: false },
         { key: 'payment_stripe_enabled', label: 'Stripe', type: 'switch', default: false },
-        { key: 'payment_balance_enabled', label: '余额支付', type: 'switch', default: false },
+        { key: 'payment_balance_enabled', label: '余额支付', type: 'switch', default: true, help: '需同时在「余额充值」启用余额功能。关闭后用户中心仍可有钱包，但结账不可用余额支付。' },
         { key: 'payment_card_pass_enabled', label: '卡密充值', type: 'switch', default: false },
         { key: 'payment_xunhupay_enabled', label: '虎皮椒', type: 'switch', default: false },
         { key: 'payment_xhpay_enabled', label: '小火付', type: 'switch', default: false },

assets/admin/src/schema/sections/payment/recharge.js

@@ -32,9 +32,9 @@ export const rechargeSchema = {
       title: '充值开关',
       icon: 'fas fa-wallet',
       fields: [
-        { key: 'pay_balance_s', label: '启用余额功能', type: 'switch', default: true },
+        { key: 'pay_balance_s', label: '启用余额功能', type: 'switch', default: true, help: '开启后用户中心显示现金钱包，并默认允许余额支付（可在收款接口单独关闭）。充值需另配支付宝/微信等外部网关。' },
         { key: 'pay_balance_desc', label: '充值说明', type: 'textarea', default: '', dependsOn: { key: 'pay_balance_s', value: true } },
-        { key: 'pay_auto_to_balance', label: '自动到账到余额', type: 'switch', default: true, dependsOn: { key: 'pay_balance_s', value: true } },
+        { key: 'pay_auto_to_balance', label: '自动到账到余额', type: 'switch', default: true, dependsOn: { key: 'pay_balance_s', value: true }, help: '充值订单支付成功后自动入账钱包（卡密/管理员调整不受此开关限制）。' },
       ],
     },
     {