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

assets/css/routes/user-center/revenue.css

@@ -85,6 +85,12 @@
   gap: 16px;
 }
 
+/* 三个 Tab 面板首屏全部直出，靠 hidden 属性做本地切换；
+ * display:grid 会覆盖 [hidden] 的 display:none，必须显式复位。 */
+.uc-reward-pane[hidden] {
+  display: none;
+}
+
 .uc-reward-pane--detail {
   grid-template-columns: repeat(2, minmax(0, 1fr));
 }