fix(wallet): 系统账户划转前自动结算 settleableUsdt，解决全额划转余额不足

## 问题
省/市区域和团队账户收到的奖励进入 settleableUsdt，
但划转验证只检查 usdtAvailable，导致全额划转报"余额不足"。

## 修复
在 requestSystemWithdrawal 事务中，划转前自动执行结算：
1. 检测账户是否为区域/团队账户（6/7/8/9开头）
2. 若 settleableUsdt > 0，自动结算到 usdtAvailable
3. 记录 REWARD_SETTLED 流水明细（含 trigger=SYSTEM_WITHDRAWAL_AUTO_SETTLE）
4. 结算和划转在同一事务中，保证原子性

## 审计流水
每次自动结算会产生一条独立的 REWARD_SETTLED 流水：
- memo: "系统账户自动结算: 待结算 X 绿积分转入可用余额（划转前自动执行）"
- payloadJson: { settledAmount, previousAvailable, newAvailable, trigger }

## 其他
- 划转白名单扩展支持 6xxx（市团队）、7xxx（省团队）
- getSystemAccountName 添加省团队/市团队名称映射

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/services/wallet-service/src/application/services/system-withdrawal-application.service.ts

@@ -95,6 +95,16 @@ export class SystemWithdrawalApplicationService {
       return `市区域(${accountSequence.substring(1)})`;
     }
 
+    // 省团队账户: 7 + 省代码
+    if (accountSequence.startsWith('7') && accountSequence.length === 7) {
+      return `省团队(${accountSequence.substring(1)})`;
+    }
+
+    // 市团队账户: 6 + 市代码
+    if (accountSequence.startsWith('6') && accountSequence.length === 7) {
+      return `市团队(${accountSequence.substring(1)})`;
+    }
+
     return `系统账户(${accountSequence})`;
   }
 
@@ -107,13 +117,8 @@ export class SystemWithdrawalApplicationService {
       return true;
     }
 
-    // 省区域账户: 9 + 省代码
-    if (accountSequence.startsWith('9') && accountSequence.length === 7) {
-      return true;
-    }
-
-    // 市区域账户: 8 + 市代码
-    if (accountSequence.startsWith('8') && accountSequence.length === 7) {
+    // 区域/团队账户: 6=市团队, 7=省团队, 8=市区域, 9=省区域
+    if (/^[6-9]\d{6}$/.test(accountSequence)) {
       return true;
     }
 
@@ -166,12 +171,60 @@ export class SystemWithdrawalApplicationService {
         throw new BadRequestException(`系统账户不存在: ${command.fromAccountSequence}`);
       }
 
-      const currentBalance = new Decimal(systemWallet.usdtAvailable.toString());
+      let currentAvailable = new Decimal(systemWallet.usdtAvailable.toString());
+      const settleableAmount = new Decimal(systemWallet.settleableUsdt?.toString() || '0');
       const withdrawAmount = new Decimal(command.amount);
 
-      if (currentBalance.lessThan(withdrawAmount)) {
+      // 6.1.1 如果是区域/团队账户且有待结算余额，先自动结算
+      // 6=市团队, 7=省团队, 8=市区域, 9=省区域 — 这些账户的奖励都进 settleableUsdt
+      const isRegionAccount = /^[6-9]/.test(command.fromAccountSequence);
+      if (isRegionAccount && settleableAmount.greaterThan(0)) {
+        this.logger.log(
+          `[SYSTEM_WITHDRAWAL] 区域账户 ${command.fromAccountSequence} 自动结算: ` +
+          `settleableUsdt=${settleableAmount.toFixed(2)} → usdtAvailable`
+        );
+
+        // 结算：settleableUsdt → usdtAvailable
+        const newAvailable = currentAvailable.plus(settleableAmount);
+        await tx.walletAccount.update({
+          where: { id: systemWallet.id },
+          data: {
+            usdtAvailable: newAvailable,
+            settleableUsdt: new Decimal(0),
+            updatedAt: new Date(),
+          },
+        });
+
+        // 记录结算流水（审计用）
+        await tx.ledgerEntry.create({
+          data: {
+            accountSequence: command.fromAccountSequence,
+            userId: systemWallet.userId,
+            entryType: LedgerEntryType.REWARD_SETTLED,
+            amount: settleableAmount,
+            assetType: 'USDT',
+            balanceAfter: newAvailable,
+            memo: `系统账户自动结算: 待结算 ${settleableAmount.toFixed(2)} 绿积分转入可用余额（划转前自动执行）`,
+            payloadJson: {
+              settledAmount: settleableAmount.toFixed(2),
+              previousAvailable: currentAvailable.toFixed(2),
+              newAvailable: newAvailable.toFixed(2),
+              trigger: 'SYSTEM_WITHDRAWAL_AUTO_SETTLE',
+            },
+          },
+        });
+
+        // 更新本地变量
+        currentAvailable = newAvailable;
+        this.logger.log(
+          `[SYSTEM_WITHDRAWAL] 自动结算完成: 可用余额 ${currentAvailable.toFixed(2)} 绿积分`
+        );
+      }
+
+      // 6.1.2 验证可用余额是否足够
+      if (currentAvailable.lessThan(withdrawAmount)) {
         throw new BadRequestException(
-          `余额不足: 当前 ${currentBalance.toFixed(2)} 绿积分, 需要 ${withdrawAmount.toFixed(2)} 绿积分`
+          `余额不足: 当前可用 ${currentAvailable.toFixed(2)} 绿积分, 需要 ${withdrawAmount.toFixed(2)} 绿积分`
         );
       }
 
@@ -179,7 +232,7 @@ export class SystemWithdrawalApplicationService {
       const orderNo = this.generateOrderNo();
 
       // 6.3 扣减系统账户余额
-      const newBalance = currentBalance.minus(withdrawAmount);
+      const newBalance = currentAvailable.minus(withdrawAmount);
       await tx.walletAccount.update({
         where: { id: systemWallet.id },
         data: {