fix(types): 修复 CI mypy strict + ruff format 失败

mypy (13 errors → 0):
- portfolio/optimizer: register_optimizer 返回类型改为 Callable 装饰器签名
  (原标注 type[WeightOptimizer] 导致 4 个子类 Too many arguments)
- factor/engine: _datetime_to_int 用 isinstance 收窄替代 object→int 强转
- factor/analysis: 删多余 type:ignore（改由 mypy override 统一处理 scipy）
- backtest/orders, execution: np.sqrt 表达式用 float() 包裹消除 no-any-return
- MyTT.pyi: MACD 签名删除错误的 LOW/HIGH 参数（与 MyTT.py 实际签名对齐）
- pyproject: 新增 scipy mypy override (ignore_missing_imports)

ruff format: 8 个 test 文件格式化

验证: 564 passed, mypy 192 文件零错误, ruff check/format 全绿

tests/unit/test_factor_base.py

@@ -1,5 +1,6 @@
 # tests/unit/test_factor_base.py
 """Test Factor base class and registry."""
+
 from __future__ import annotations
 
 import pandas as pd
@@ -97,6 +98,7 @@ class TestRegistry:
                 return df["close"]
 
         with pytest.raises(ValueError, match="已注册"):
+
             @register_factor
             class Dup2(Factor):
                 name = "dup_test_factor"