feat: 微服务架构拆分和前后端优化

后端:
- 拆分出 agent_service, runtime_service, trading_service, news_service
- Gateway 模块化拆分 (gateway_*.py)
- 添加 domains/ 领域层
- 新增 control_client, runtime_client
- 更新 start-dev.sh 支持 split 服务模式

前端:
- 完善 API 服务层 (newsApi, tradingApi)
- 更新 vite.config.js
- Explain 组件优化

测试:
- 添加多个服务 app 测试

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

backend/tests/test_provider_router.py

@@ -9,6 +9,7 @@ def test_router_includes_local_csv_fallback(monkeypatch):
     monkeypatch.delenv("FINNHUB_API_KEY", raising=False)
     monkeypatch.delenv("FINANCIAL_DATASETS_API_KEY", raising=False)
     monkeypatch.delenv("FIN_DATA_SOURCE", raising=False)
+    monkeypatch.delenv("ENABLED_DATA_SOURCES", raising=False)
     reset_config()
 
     router = DataProviderRouter()