feat(strategy): 新增纯美股动量轮动策略

新增美股轮动策略模块:
- strategies/us_rotation/config.yaml: 47只美股标的池，动量窗口250天，Top5选股
- strategies/us_rotation/strategy.py: USRotationStrategy实现
- run_us_rotation.py: 回测入口脚本

回测结果 (2016-2026, 约10年):
- 总收益: 7675% (年化52.49%)
- 基准NDX收益: 540% (年化19.72%)
- 超额年化收益: 32.78%
- 夏普比率: 1.33 (基准0.80)
- 最大回撤: 42.15%
- 卡玛比率: 1.25
- 胜率: 56.1%
- 平均持仓: 2.7天

年度最佳: 2020年+221% (超额176%)
年度防守: 2022年-10.5% (基准-33.7%, 超额+23.3%)

持仓Top5: NVDA(35.8%), AMD(30.1%), SHOP(26%), AVGO(23.9%), FICO(23.3%)

strategies/us_rotation/config.yaml

@@ -0,0 +1,194 @@
+# 美股轮动策略配置
+
+# ==================== 候选池配置 ====================
+code_list:
+  # 科技巨头
+  "AAPL":
+    name: "Apple"
+    sector: "Technology"
+  "ADBE":
+    name: "Adobe"
+    sector: "Technology"
+  "AMD":
+    name: "AMD"
+    sector: "Technology"
+  "AMZN":
+    name: "Amazon"
+    sector: "Technology"
+  "ASML":
+    name: "ASML"
+    sector: "Technology"
+  "AVGO":
+    name: "Broadcom"
+    sector: "Technology"
+  "CRM":
+    name: "Salesforce"
+    sector: "Technology"
+  "CRWD":
+    name: "CrowdStrike"
+    sector: "Technology"
+  "CSCO":
+    name: "Cisco"
+    sector: "Technology"
+  "FICO":
+    name: "FICO"
+    sector: "Technology"
+  "GOOGL":
+    name: "Google"
+    sector: "Technology"
+  "INTC":
+    name: "Intel"
+    sector: "Technology"
+  "KLAC":
+    name: "KLA"
+    sector: "Technology"
+  "LRCX":
+    name: "Lam Research"
+    sector: "Technology"
+  "META":
+    name: "Meta"
+    sector: "Technology"
+  "MSFT":
+    name: "Microsoft"
+    sector: "Technology"
+  "MU":
+    name: "Micron"
+    sector: "Technology"
+  "NET":
+    name: "Cloudflare"
+    sector: "Technology"
+  "NFLX":
+    name: "Netflix"
+    sector: "Technology"
+  "NVDA":
+    name: "NVIDIA"
+    sector: "Technology"
+  "ORCL":
+    name: "Oracle"
+    sector: "Technology"
+  "PANW":
+    name: "Palo Alto"
+    sector: "Technology"
+  "PLTR":
+    name: "Palantir"
+    sector: "Technology"
+  "QCOM":
+    name: "Qualcomm"
+    sector: "Technology"
+  "SNOW":
+    name: "Snowflake"
+    sector: "Technology"
+  "TSLA":
+    name: "Tesla"
+    sector: "Technology"
+  "TSM":
+    name: "TSMC"
+    sector: "Technology"
+  
+  # 金融
+  "AXP":
+    name: "American Express"
+    sector: "Financial"
+  "BAC":
+    name: "Bank of America"
+    sector: "Financial"
+  "C":
+    name: "Citigroup"
+    sector: "Financial"
+  "GS":
+    name: "Goldman Sachs"
+    sector: "Financial"
+  "JPM":
+    name: "JPMorgan"
+    sector: "Financial"
+  "MA":
+    name: "Mastercard"
+    sector: "Financial"
+  "MS":
+    name: "Morgan Stanley"
+    sector: "Financial"
+  
+  # 消费零售
+  "COST":
+    name: "Costco"
+    sector: "Consumer"
+  "LULU":
+    name: "Lululemon"
+    sector: "Consumer"
+  "PDD":
+    name: "PDD Holdings"
+    sector: "Consumer"
+  "SHOP":
+    name: "Shopify"
+    sector: "Consumer"
+  
+  # 医药健康
+  "LLY":
+    name: "Eli Lilly"
+    sector: "Healthcare"
+  "NVO":
+    name: "Novo Nordisk"
+    sector: "Healthcare"
+  
+  # 其他
+  "CAT":
+    name: "Caterpillar"
+    sector: "Industrial"
+  "COIN":
+    name: "Coinbase"
+    sector: "Crypto"
+  "CRCL":
+    name: "Circle"
+    sector: "Crypto"
+  "FUTU":
+    name: "Futu"
+    sector: "Financial"
+  "HOOD":
+    name: "Robinhood"
+    sector: "Financial"
+  "SAP":
+    name: "SAP"
+    sector: "Technology"
+  "SCCO":
+    name: "Southern Copper"
+    sector: "Materials"
+
+# ==================== 基准配置 ====================
+benchmark:
+  code: "NDX"
+  name: "纳斯达克100"
+
+# ==================== 回测参数 ====================
+start_date: "2016-01-01"
+
+# ==================== 因子参数 ====================
+# 动量窗口（天数）
+n_days: 250
+# 因子类型
+factor_type: "momentum"
+
+# ==================== 轮动参数 ====================
+# 不分组，直接选 Top N
+diversified: false
+select_num: 5
+
+# ==================== 调仓控制 ====================
+# 每日调仓
+rebalance_days: 1
+# 调仓阈值：新组合得分超过当前组合 X% 才触发调仓
+rebalance_threshold: 0.0
+# 交易成本（双边）
+trade_cost: 0.001
+
+# ==================== 数据缓存 ====================
+use_cache: true
+
+# ==================== 数据源配置 ====================
+# SSH 隧道配置（用于 yfinance）
+ssh_tunnel:
+  enabled: true
+  host: "8.218.167.69"
+  port: 22
+  username: "root"
+  key_path: "hk_ecs.pem"
+  local_port: 1080