feat(withdrawal): make payout channels a configurable sortable list

The payout channel was a two-item checkbox (alipay / wechat). Sites that pay
out through a bank transfer, USDT or any other route had no way to express it,
and every surface behind it — the withdrawal modal, the server-side check, the
admin review list — hard-coded those two names.

affiliate_payout_channels is now a repeater on both the PHP and Vue schemas,
using the same draggable component as the post filters and gateway config. Each
row carries a stable key, a display label, an account placeholder, an optional
note and an enabled flag. Disabled channels disappear from the front end but
stay resolvable, so historical withdrawal records still render their original
name.

PaymentRuntime::payout_channels() normalises the stored structure: it drops rows
with an empty key or label, de-duplicates keys, and falls back to the built-in
two channels when nothing is configured. enabled_payout_channels() feeds the
front end and payout_channel() resolves a single key for record display.
CommissionLedger's validation now compares against the configured, enabled keys
instead of a literal allowlist.

The withdrawal modal renders the configured list and swaps the account
placeholder and note when the channel changes; credits.js drives that. The
admin review page reads the same settings for its method labels and filter, and
the review dialog gained a "渠道说明" row so the operator sees the payout
instruction, hidden when empty.

Default channels live in SchemaPayment as plain data — the runtime imports them
rather than the reverse, because the schema layer must not depend on a runtime
settings class (doing it the other way made the schema harness fatal).

Verification: drove payout_channels() through default / custom / dirty / duplicate
inputs and confirmed enabled filtering, note lookup and disabled-channel
resolution. Added payment-withdrawal-channels-contract.test.cjs covering the
schema shape, runtime helpers, front-end wiring and admin read path. 873 tests
pass, PSR-4 audit clean, admin SPA builds.

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

@@ -1,6 +1,14 @@
 /**
  * 提现策略 — 提现门槛、每日限制、收款渠道与提现协议。
  */
+
+/** 默认收款渠道：支付宝与微信，与参考主题一致。 */
+export function defaultPayoutChannels() {
+  return [
+    { key: 'alipay', label: '支付宝收款码', account_hint: '姓名 + 支付宝账号', note: '', enabled: true },
+    { key: 'wechat', label: '微信收款码', account_hint: '姓名 + 微信号', note: '', enabled: true },
+  ]
+}
 export const withdrawalSchema = {
   key: 'payment.withdrawal',
   title: '提现策略',
@@ -12,7 +20,7 @@ export const withdrawalSchema = {
     affiliate_daily_withdrawal_count: 3,
     affiliate_daily_withdrawal_limit: '500.00',
     affiliate_withdrawal_reset_time: '00:00',
-    affiliate_payout_channels: ['alipay', 'wechat'],
+    affiliate_payout_channels: defaultPayoutChannels(),
     pay_rebate_withdraw_text_details: '<div>可提现金额达到50元后即可发起提现</div><div>申请提现需后台人工处理，一般2-3小时，请耐心等待</div><div>如有其它疑问，请与客服联系</div>',
   },
   groups: [
@@ -40,7 +48,21 @@ export const withdrawalSchema = {
       title: '收款渠道',
       icon: 'fa fas fa-qrcode',
       fields: [
-        { key: 'affiliate_payout_channels', label: '可用收款渠道', type: 'checkbox', default: ['alipay', 'wechat'], sanitize_type: 'array', options: [{ label: '支付宝收款码', value: 'alipay' }, { label: '微信收款码', value: 'wechat' }] },
+        {
+          key: 'affiliate_payout_channels',
+          label: '收款渠道',
+          type: 'repeater',
+          addText: '添加收款渠道',
+          default: defaultPayoutChannels(),
+          description: '用户提现时可选择的收款方式，可拖拽排序、自定义名称。停用的渠道不会在前台展示，但历史提现记录仍按原名称显示。',
+          fields: [
+            { key: 'key', label: '渠道标识', type: 'input', default: '', help: '英文小写，用于区分渠道（如 alipay、wechat、bank）。保存后请勿随意修改，历史提现记录依赖它。' },
+            { key: 'label', label: '渠道名称', type: 'input', default: '', help: '前台下拉里显示的名称，可自定义。' },
+            { key: 'account_hint', label: '收款信息提示', type: 'input', default: '', help: '用户填写收款账户时的占位提示，如「姓名 + 支付宝账号」。' },
+            { key: 'note', label: '渠道说明', type: 'textarea', default: '', rows: 2, help: '选中该渠道时在收款信息下方展示的补充说明，可留空。' },
+            { key: 'enabled', label: '启用', type: 'switch', default: true },
+          ],
+        },
       ],
     },
     {