- Critical 1: initialize orders=[] before loop to prevent NameError when df is empty
- Critical 2: replace bare sqlite3 conn with context manager (with statement) in get_signal
- Critical 3: remove ticker param from _load_best_params (table has no ticker col, params are global)
- Important: extract db_path as self._db_path attribute in __init__ (DRY)
- Important: add comment explaining lazy imports require sys.path set in __init__
陈少杰