fix(transfer): 修复积分股划转到分配账户失败问题

后端:
- transfer.service.ts: Error → BadRequestException，业务错误返回HTTP 400而非500
- transfer.controller.ts: Error → UnauthorizedException，正确返回HTTP 401
- 错误信息改为中文：余额不足、账户不存在等提示更明确

前端:
- asset_display.dart: 新增 tradingAvailableShares 计算属性（总可用 - 挖矿可用）
- trading_page.dart: 划转弹窗显示可用余额（扣除冻结）而非总余额
- trading_page.dart: 划转失败时显示后端具体错误信息而非通用提示

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

backend/services/trading-service/src/api/controllers/transfer.controller.ts

@@ -1,4 +1,4 @@
-import { Controller, Get, Post, Param, Query, Body, Req } from '@nestjs/common';
+import { Controller, Get, Post, Param, Query, Body, Req, UnauthorizedException } from '@nestjs/common';
 import { ApiTags, ApiOperation, ApiResponse, ApiBearerAuth, ApiQuery } from '@nestjs/swagger';
 import { IsString } from 'class-validator';
 import { TransferService } from '../../application/services/transfer.service';
@@ -19,7 +19,7 @@ export class TransferController {
   async transferIn(@Body() dto: TransferDto, @Req() req: any) {
     const accountSequence = req.user?.accountSequence;
     if (!accountSequence) {
-      throw new Error('Unauthorized');
+      throw new UnauthorizedException('未登录');
     }
 
     return this.transferService.transferIn(accountSequence, dto.amount);
@@ -30,7 +30,7 @@ export class TransferController {
   async transferOut(@Body() dto: TransferDto, @Req() req: any) {
     const accountSequence = req.user?.accountSequence;
     if (!accountSequence) {
-      throw new Error('Unauthorized');
+      throw new UnauthorizedException('未登录');
     }
 
     return this.transferService.transferOut(accountSequence, dto.amount);
@@ -47,7 +47,7 @@ export class TransferController {
   ) {
     const accountSequence = req.user?.accountSequence;
     if (!accountSequence) {
-      throw new Error('Unauthorized');
+      throw new UnauthorizedException('未登录');
     }
 
     return this.transferService.getTransferHistory(accountSequence, page ?? 1, pageSize ?? 50);

backend/services/trading-service/src/application/services/transfer.service.ts

@@ -1,4 +1,4 @@
-import { Injectable, Logger } from '@nestjs/common';
+import { Injectable, Logger, BadRequestException } from '@nestjs/common';
 import { ConfigService } from '@nestjs/config';
 import { TradingAccountRepository } from '../../infrastructure/persistence/repositories/trading-account.repository';
 import { PrismaService } from '../../infrastructure/persistence/prisma/prisma.service';
@@ -27,7 +27,7 @@ export class TransferService {
     const transferAmount = new Money(amount);
 
     if (transferAmount.value.lessThan(this.minTransferAmount)) {
-      throw new Error(`Minimum transfer amount is ${this.minTransferAmount}`);
+      throw new BadRequestException(`最低划转数量为 ${this.minTransferAmount}`);
     }
 
     const transferNo = this.generateTransferNo();
@@ -48,7 +48,7 @@ export class TransferService {
       const response = await this.callMiningServiceTransferOut(accountSequence, amount, transferNo);
 
       if (!response.success) {
-        throw new Error(response.message || 'Mining service transfer failed');
+        throw new BadRequestException(response.message || '挖矿服务划转失败');
       }
 
       // 增加交易账户余额
@@ -94,16 +94,16 @@ export class TransferService {
     const transferAmount = new Money(amount);
 
     if (transferAmount.value.lessThan(this.minTransferAmount)) {
-      throw new Error(`Minimum transfer amount is ${this.minTransferAmount}`);
+      throw new BadRequestException(`最低划转数量为 ${this.minTransferAmount}`);
     }
 
     const account = await this.accountRepository.findByAccountSequence(accountSequence);
     if (!account) {
-      throw new Error('Trading account not found');
+      throw new BadRequestException('交易账户不存在');
     }
 
     if (account.availableShares.isLessThan(transferAmount)) {
-      throw new Error('Insufficient available shares');
+      throw new BadRequestException('可用积分股不足（部分积分股可能已被 C2C 订单冻结）');
     }
 
     const transferNo = this.generateTransferNo();
@@ -131,7 +131,7 @@ export class TransferService {
         // 回滚交易账户余额
         account.transferSharesIn(transferAmount, `${transferNo}_rollback`);
         await this.accountRepository.save(account);
-        throw new Error(response.message || 'Mining service transfer failed');
+        throw new BadRequestException(response.message || '挖矿服务划转失败');
       }
 
       // 更新划转记录

frontend/mining-app/lib/domain/entities/asset_display.dart

@@ -67,6 +67,14 @@ class AssetDisplay extends Equatable {
     required this.totalSold,
   });
 
+  /// 交易账户可用积分股（扣除冻结部分）= 总可用积分股 - 挖矿账户可用积分股
+  String get tradingAvailableShares {
+    final totalAvailable = double.tryParse(availableShares) ?? 0;
+    final miningAvailable = double.tryParse(miningShareBalance) ?? 0;
+    final result = totalAvailable - miningAvailable;
+    return result < 0 ? '0' : result.toStringAsFixed(8);
+  }
+
   /// 总积分股余额 = 可用 + 冻结
   String get totalShareBalance {
     final available = double.tryParse(availableShares) ?? 0;

frontend/mining-app/lib/presentation/pages/trading/trading_page.dart

@@ -402,8 +402,10 @@ class _TradingPageState extends ConsumerState<TradingPage> {
 
     // 挖矿账户积分股（可划转卖出）
     final miningShareBalance = asset?.miningShareBalance ?? '0';
-    // 交易账户积分股（可直接卖出）
+    // 交易账户积分股总余额（含冻结，用于显示）
     final tradingShareBalance = asset?.tradingShareBalance ?? '0';
+    // 交易账户可用积分股（扣除冻结，用于划转）
+    final tradingAvailableShares = asset?.tradingAvailableShares ?? '0';
     // 可用积分股（总计：挖矿 + 交易）
     final availableShares = asset?.availableShares ?? '0';
     // 可用积分值（现金）
@@ -612,7 +614,7 @@ class _TradingPageState extends ConsumerState<TradingPage> {
               Align(
                 alignment: Alignment.centerRight,
                 child: GestureDetector(
-                  onTap: () => _showTransferDialog(miningShareBalance, tradingShareBalance),
+                  onTap: () => _showTransferDialog(miningShareBalance, tradingAvailableShares),
                   child: const Text(
                     '划转',
                     style: TextStyle(
@@ -1626,9 +1628,10 @@ class _TransferBottomSheetState extends ConsumerState<_TransferBottomSheet> {
             ),
           );
         } else {
+          final errorMsg = ref.read(tradingNotifierProvider).error ?? '划转失败，请稍后重试';
           ScaffoldMessenger.of(context).showSnackBar(
-            const SnackBar(
+            SnackBar(
-              content: Text('划转失败，请稍后重试'),
+              content: Text(errorMsg),
               backgroundColor: Colors.red,
             ),
           );