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[mondi04]

Closes #928

SelectChoice and Choice had no disabled field, making it impossible
to render <option disabled> without workarounds via render_kw.

What this patch does

• Adds disabled: bool = False to SelectChoice and Choice
• Propagates disabled through iter_choices() and iter_groups()
• Select.render_option renders the disabled HTML attribute when set

Usage

SelectField(choices=[
    SelectChoice("a", "Option A"),
    SelectChoice("b", "Option B", disabled=True),
])

Checklist

• Tests added that fail without the patch
• All tests pass with pytest