Auto-prefill form fields from SQLAlchemy model defaults

[LoveBloodAndDiamonds]

Is your feature request related to a problem? Please describe.

Currently, when creating a new record via Starlette Admin, all form fields are empty by default, even if the SQLAlchemy model defines default values (either through default= or server_default=). This means users have to manually fill in values that should already have sensible defaults.

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Describe the solution you’d like

I would like Starlette Admin to automatically prefill form fields with the default values defined in the SQLAlchemy model.
For example, when a user clicks “Create” for a model, the form should already display those default values, similar to how sqladmin handles this.

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Describe alternatives you’ve considered

Manually overriding form fields and setting initial values in a custom view.

[jowilf]

#503