[Bug]: `input_date()` defaults to today on the _server_ (not client)

[cpsievert]

Introduced by https://github.com/posit-dev/py-shiny/pull/1920/files#diff-d8cf041312c78c75d66cb8d697899fa5f8b7fd45ec675673ba739f2eadf7d6f3

With that change, input_date() and input_date_range() started defaulting to the server's current date (not the client's)

cc @karangattu @schloerke