remove mutable param

[zhibindai26]

• Fix mutable default argument (params={}) in PortfolioSizeService.retrieve(), PropertyTypeService.retrieve(), and PropertyEventsService.retrieve()
• The shared default dict caused portfolio_size and property_type values to silently leak into subsequent calls that omitted the params argument
• Changed to idiomatic params=None with if params is None: params = {} guard in the function body
• Changed from deprecated config to ConfigDict in pydantic model configs