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/Core/DBMigratorPart2.php

@@ -435,6 +435,8 @@ trait DBMigratorPart2 {
         dbDelta($sql_affiliate_relation);
 
         // ── immutable commission ledger ──
+        // 佣金即时入账（无冻结/结算期）：下单支付即 credit 到 COMMISSION 资金池，
+        // 本表仅作佣金明细账 + 退款冲正的溯源记录。status: credited | cancelled。
         $sql_commission_ledger = "CREATE TABLE {$prefix}aksrt_commission_ledger (
             id BIGINT UNSIGNED NOT NULL AUTO_INCREMENT,
             promoter_id BIGINT UNSIGNED NOT NULL,
@@ -445,12 +447,10 @@ trait DBMigratorPart2 {
             ratio DECIMAL(8,4) NOT NULL DEFAULT 0,
             original_amount DECIMAL(18,2) NOT NULL DEFAULT 0,
             adjustment_total DECIMAL(18,2) NOT NULL DEFAULT 0,
-            status VARCHAR(20) NOT NULL DEFAULT 'pending',
+            status VARCHAR(20) NOT NULL DEFAULT 'credited',
             idempotency_key VARCHAR(128) NOT NULL,
 			cancel_operation_key VARCHAR(191) DEFAULT NULL,
 			cancel_payload_hash CHAR(64) DEFAULT NULL,
-            available_at DATETIME NOT NULL,
-            settled_at DATETIME DEFAULT NULL,
             created_at DATETIME NOT NULL,
             note TEXT DEFAULT NULL,
             PRIMARY KEY (id),
@@ -458,11 +458,20 @@ trait DBMigratorPart2 {
 			UNIQUE KEY uniq_commission_cancel_operation (cancel_operation_key),
             KEY idx_promoter_status (promoter_id, status),
             KEY idx_order_type (order_number, order_type),
-            KEY idx_available (status, available_at),
             KEY idx_created (created_at)
         ) ENGINE=InnoDB {$charset_collate};";
         dbDelta($sql_commission_ledger);
 
+        // 佣金欠款挂账：退款全额收回后，若佣金池不足产生的差额记为欠款，
+        // 后续新增佣金先抵扣欠款再入池。每用户一行。
+        $sql_commission_debt = "CREATE TABLE {$prefix}aksrt_commission_debt (
+            user_id BIGINT UNSIGNED NOT NULL,
+            debt_minor BIGINT UNSIGNED NOT NULL DEFAULT 0,
+            updated_at DATETIME NOT NULL,
+            PRIMARY KEY (user_id)
+        ) ENGINE=InnoDB {$charset_collate};";
+        dbDelta($sql_commission_debt);
+
         // ── immutable commission adjustments (refund/debt/manual) ──
         $sql_commission_adjustment = "CREATE TABLE {$prefix}aksrt_commission_adjustment (
             id BIGINT UNSIGNED NOT NULL AUTO_INCREMENT,