TapCardViewWidget does not notify when input is cleared

[imedhat99]

Issue Summary

TapCardViewWidget triggers onValidInput only when card input becomes valid
When the user clears the card input (e.g. using the ❌ clear button), no callback is triggered
This causes the application state to remain marked as valid even though the input is now empty or invalid.

Steps to Reproduce

• Integrate TapCardViewWidget in a Flutter application
• Listen to onValidInput to update the card validity state
• Enter valid card details and confirm onValidInput is triggered
• Clear the card input using the ❌ (clear) button
• Observe that no callback is triggered after clearing the input

Expected Behavior

• The SDK should notify the host application when:
• Card input becomes invalid
• Card input is cleared
• This could be provided via:
• An onInvalidInput callback
• An onInputChange callback with validation state
• Or a validation boolean parameter

Actual Behavior

• onValidInput is triggered only on successful validation
• No callback is fired when:
• Input is cleared
• Input becomes invalid
• Application state remains unchanged unless handled manually

Impact

• Pay / Submit button may remain enabled after clearing the card input
• Validation state becomes inconsistent with the actual card input
• Requires workarounds such as focus listeners or manual state resets