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_transform.py

@@ -1,5 +1,6 @@
 # tests/unit/test_factor_transform.py
 """Test factor preprocessing functions."""
+
 from __future__ import annotations
 
 import numpy as np
@@ -20,12 +21,14 @@ def _make_cross_section(n_dates: int = 20, n_stocks: int = 30, seed: int = 42) -
     rows = []
     for d in range(n_dates):
         for s in range(n_stocks):
-            rows.append({
-                "date": 20240101 + d,
-                "code": f"{s:06d}",
-                "momentum_20d": rng.normal(0.02, 0.05),
-                "volatility_20d": abs(rng.normal(0.02, 0.01)),
-            })
+            rows.append(
+                {
+                    "date": 20240101 + d,
+                    "code": f"{s:06d}",
+                    "momentum_20d": rng.normal(0.02, 0.05),
+                    "volatility_20d": abs(rng.normal(0.02, 0.01)),
+                }
+            )
     df = pd.DataFrame(rows)
     df.loc[0, "momentum_20d"] = 10.0
     df.loc[1, "momentum_20d"] = -10.0