fix: support isolated Python startup

dev.bat

@@ -0,0 +1,3 @@
+title run
+cd /d "%~dp0src" && python main.py
+pause

src/main.py

@@ -1,5 +1,10 @@
 import logging
 import sys
+from pathlib import Path
+
+SRC_DIR = Path(__file__).resolve().parent
+if str(SRC_DIR) not in sys.path:
+    sys.path.insert(0, str(SRC_DIR))
 
 from PySide6.QtWidgets import QApplication