Add date input tests to TagHelperModelBindingTests

[Copilot]

Adds integration tests for date input tag helper model binding, following the existing pattern for text input and password input tests.

Changes:

• Added DateInput_RendersCorrectly and DateInputOverridden_RendersCorrectly test methods
• Added DateInputTestsModel with DateOnly? property and Display attributes
• Added controller actions and Razor views for both test cases
• Removed debug PauseAsync() call from TextInputOverridden_RendersCorrectly

Key difference from text/password inputs:
Date input IDs use dot notation when overriding the id attribute:

// With id="OverriddenId", the individual inputs get:
Assert.Equal("OverriddenId.Day", dayInput.GetAttributeAsync("id"));    // Not "OverriddenId-day"
Assert.Equal("OverriddenId.Month", monthInput.GetAttributeAsync("id"));
Assert.Equal("OverriddenId.Year", yearInput.GetAttributeAsync("id"));

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