feat(revenue): immediate commission credit with independent withdrawable pool

Aligns affiliate commission with the reference theme: commission is credited
to a dedicated COMMISSION asset pool the moment an order is paid, removing the
7-day settlement freeze, the settlement cron, and the settlement_days setting.

- Ledger: add AssetType::COMMISSION (isolated from the recharge balance wallet)
- CommissionLedger: credit-on-record + opportunistic debt repayment; refunds
  claw back the full commission from the pool, carrying any shortfall as debt
  (aksrt_commission_debt) that future commission pays down first
- Withdrawal: make asset-aware via a source discriminator (commission vs
  balance); each pool keeps independent daily limits, pending gate, and
  reject-refund. Balance withdrawal (recharge + creator income) is unchanged
- Fix pay_rebate_self_s: honor self-commission at purchase time
- Revenue card: show pool balance + 累计/已提现 (drop 待结算), debt when present
- Schema 2.0.0 -> 2.1.0: add commission_debt, drop freeze columns

src/Admin/Schema/SchemaPayment.php

@@ -347,7 +347,6 @@ class SchemaPayment {
 									['key' => 'pay_rebate_ratio_vip_2', 'label' => '二级会员返佣比例(%)', 'type' => 'number', 'default' => 20, 'min' => 0, 'max' => 100, 'dependsOn' => ['key' => 'pay_rebate_s', 'value' => true]],
 								]],
 							]],
-							['key' => 'affiliate_settlement_days', 'label' => '结算观察期(天)', 'type' => 'number', 'default' => 7, 'min' => 0, 'max' => 90, 'dependsOn' => ['key' => 'pay_rebate_s', 'value' => true], 'help' => '订单完成后经过观察期，佣金才会结算到可提现余额'],
 							['key' => 'affiliate_disabled_code_stops_commission', 'label' => '推广码禁用后停止返佣', 'type' => 'switch', 'default' => false, 'dependsOn' => ['key' => 'pay_rebate_s', 'value' => true], 'help' => '开启后，推广者的推广码被禁用（或缺失）时，其名下已绑定用户的新订单不再产生佣金；关闭则绑定关系继续生效'],
 						]],
 						['key' => 'text', 'title' => '返佣文案', 'fields' => [