fix: show pip install errors in start.bat and loosen dependency pins for Python 3.13+

start.bat was silently swallowing pip errors. Strict version pins on
pydantic, fastapi, and uvicorn caused build failures on Python 3.13+
due to missing pre-built wheels.


Former-commit-id: 7b4e907bd6

start.bat

@@ -12,7 +12,7 @@ if not exist "venv\" (
     python -m venv venv
 )
 call venv\Scripts\activate.bat
-pip install -r requirements.txt >nul 2>&1
+pip install -r requirements.txt
 cd ..
 
 echo.