feat: Add AI model config hot-reload support (TDD)

[xqliu]

Summary

Implements AI model configuration hot-reload functionality to allow updating AI model settings (API keys, model names, URLs) without requiring container restarts. This makes the database-driven configuration system fully functional.

Implementation Approach

• TDD methodology: Tests written first, then implementation
• KISS principle: Simple, focused solution (Solution 1 from issue discussion)
• Scope: Updates only AI model-related configuration fields

Changes Made

Core Implementation

• trader/auto_trader.go:
  • Added ReloadAIModelConfig() method to update AI config from database
  • Added reinitializeMCPClient() helper to apply new settings to MCP client
  • Supports DeepSeek, Qwen, and custom AI providers
  • Fixed Go 1.25 compilation warnings (log.Printf → log.Print)

Test Coverage

• trader/config_reload_test.go (4 comprehensive tests):
  • ✅ TestReloadAIModelConfig: Basic hot-reload with API key and model name update
  • ✅ TestReloadAIModelConfig_EmptyModelName: Empty model name handling
  • ✅ TestReloadAIModelConfig_QwenModel: Qwen-specific configuration
  • ✅ TestReloadAIModelConfig_PreservesOtherConfig: Ensures non-AI config unchanged

Test Results

=== RUN   TestReloadAIModelConfig
--- PASS: TestReloadAIModelConfig (0.00s)
=== RUN   TestReloadAIModelConfig_EmptyModelName
--- PASS: TestReloadAIModelConfig_EmptyModelName (0.00s)
=== RUN   TestReloadAIModelConfig_QwenModel
--- PASS: TestReloadAIModelConfig_QwenModel (0.00s)
=== RUN   TestReloadAIModelConfig_PreservesOtherConfig
--- PASS: TestReloadAIModelConfig_PreservesOtherConfig (0.00s)
PASS
ok      nofx/trader     0.007s

Next Steps

The ReloadAIModelConfig() method is implemented and tested but not yet integrated into the system. Future work may include:

• Adding API endpoint to trigger reload
• Automatic reload before each AI decision
• Reload on database change notification

Closes #248

🤖 Generated with Claude Code

[xqliu]

经过进一步分析，发现当前系统已经实现了配置更新功能：

在 api/server.go:640-645 的 handleUpdateModelConfigs 中：

// 重新加载该用户的所有交易员，使新配置立即生效
err := s.traderManager.LoadUserTraders(s.database, userID)

现有行为：

• 用户修改 AI 模型配置后，系统会调用 LoadUserTraders
• 这会停止旧的 trader 实例，并用新配置重新创建 trader
• 配置更新立即生效，无需手动重启容器

与本 PR 的区别：

• 现有方式：重新创建 trader（相当于重启 trader）
• 本 PR 方式：热更新现有 trader 实例（不重启）

结论：
虽然现有方式会重启 trader，但对于 3 分钟扫描周期的交易系统来说，影响可以忽略。热更新的优化收益不大，暂不需要此功能。

关闭此 PR 和对应的 Issue #248。