fix(c2c): 修复水单上传权限、手机号显示、卖方ID显示

- Dockerfile 预创建 /app/uploads/c2c-proofs 并设置正确权限
- JWT guard 从 token payload 提取 phone 字段（之前仅提取 accountSequence）
- 订单详情页订单信息组新增卖方ID显示

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

backend/services/trading-service/Dockerfile

@@ -24,7 +24,7 @@ RUN addgroup --system --gid 1001 nodejs && \
 
 RUN apk add --no-cache curl tzdata openssl
 
-RUN mkdir -p /app && chown nestjs:nodejs /app
+RUN mkdir -p /app /app/uploads/c2c-proofs && chown -R nestjs:nodejs /app
 WORKDIR /app
 
 USER nestjs

backend/services/trading-service/src/shared/guards/jwt-auth.guard.ts

@@ -24,7 +24,10 @@ export class JwtAuthGuard implements CanActivate {
     try {
       const secret = this.configService.get<string>('JWT_SECRET', 'default-secret');
       const payload = jwt.verify(token, secret) as any;
-      request.user = { accountSequence: payload.sub };
+      request.user = {
+        accountSequence: payload.sub,
+        phone: payload.phone,
+      };
       return true;
     } catch {
       throw new UnauthorizedException('Invalid token');

frontend/mining-app/lib/presentation/pages/c2c/c2c_order_detail_page.dart

@@ -346,6 +346,11 @@ class _C2cOrderDetailPageState extends ConsumerState<C2cOrderDetailPage> {
           ),
           const SizedBox(height: 16),
           _buildInfoRow('订单编号', order.orderNo, canCopy: true),
+          // 卖方收款ID（卖单=maker，买单=taker）
+          if (order.isSell)
+            _buildInfoRow('卖方ID', order.makerAccountSequence, canCopy: true)
+          else if (order.takerAccountSequence != null)
+            _buildInfoRow('卖方ID', order.takerAccountSequence!, canCopy: true),
           _buildInfoRow('单价', '${formatPrice(order.price)} 积分值'),
           _buildInfoRow('数量', '${formatAmount(order.quantity)} 积分值'),
           _buildInfoRow('总金额', '${formatAmount(order.totalAmount)} 积分值'),