Handle margin shortfall by resizing positions

[MarsDoge]

Pull Request - Backend | 后端 PR

💡 提示 Tip: 推荐 PR 标题格式 type(scope): description
例如: feat(trader): add new strategy | fix(api): resolve auth issue

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📝 Description | 描述

English: ｜ 中文：

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🎯 Type of Change | 变更类型

• 🐛 Bug fix | 修复 Bug
• ✨ New feature | 新功能
• 💥 Breaking change | 破坏性变更
• ♻️ Refactoring | 重构
• ⚡ Performance improvement | 性能优化
• 🔒 Security fix | 安全修复
• 🔧 Build/config change | 构建/配置变更

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🔗 Related Issues | 相关 Issue

• Closes # | 关闭 #
• Related to # | 相关 #

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📋 Changes Made | 具体变更

English: ｜ 中文：

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🧪 Testing | 测试

Test Environment | 测试环境

• OS | 操作系统:
• Go Version | Go 版本:
• Exchange | 交易所: [if applicable | 如适用]

Manual Testing | 手动测试

• Tested locally | 本地测试通过
• Tested on testnet | 测试网测试通过（交易所集成相关）
• Unit tests pass | 单元测试通过
• Verified no existing functionality broke | 确认没有破坏现有功能

Test Results | 测试结果

Test output here | 测试输出

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🔒 Security Considerations | 安全考虑

• No API keys or secrets hardcoded | 没有硬编码 API 密钥
• User inputs properly validated | 用户输入已正确验证
• No SQL injection vulnerabilities | 无 SQL 注入漏洞
• Authentication/authorization properly handled | 认证/授权正确处理
• Sensitive data is encrypted | 敏感数据已加密
• N/A (not security-related) | 不适用

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⚡ Performance Impact | 性能影响

• No significant performance impact | 无显著性能影响
• Performance improved | 性能提升
• Performance may be impacted (explain below) | 性能可能受影响

If impacted, explain | 如果受影响，请说明：

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✅ Checklist | 检查清单

Code Quality | 代码质量

• Code follows project style | 代码遵循项目风格
• Self-review completed | 已完成代码自查
• Comments added for complex logic | 已添加必要注释
• Code compiles successfully | 代码编译成功 (go build)
• Ran go fmt | 已运行 go fmt

Documentation | 文档

• Updated relevant documentation | 已更新相关文档
• Added inline comments where necessary | 已添加必要的代码注释
• Updated API documentation (if applicable) | 已更新 API 文档

Git

• Commits follow conventional format | 提交遵循 Conventional Commits 格式
• Rebased on latest dev branch | 已 rebase 到最新 dev 分支
• No merge conflicts | 无合并冲突

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📚 Additional Notes | 补充说明

English: ｜ 中文：

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By submitting this PR, I confirm | 提交此 PR，我确认：

• I have read the Contributing Guidelines | 已阅读贡献指南
• I agree to the Code of Conduct | 同意行为准则
• My contribution is licensed under AGPL-3.0 | 贡献遵循 AGPL-3.0 许可证

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🌟 Thank you for your contribution! | 感谢你的贡献！

[github-actions]

🔧 已自动应用专用模板 | Auto-Applied Template

检测到您的PR主要包含 backend 相关的变更，系统已自动为您应用相应的模板。

Detected that your PR primarily contains backend changes. The appropriate template has been automatically applied.

文件统计 | File Statistics

• 🔧 Go files: 2

已应用模板 | Applied Template
.github/PULL_REQUEST_TEMPLATE/backend.md

✨ 您现在可以直接在PR描述中填写相关信息了！

✨ You can now fill in the relevant information in the PR description!