fix: disable generate invoice button when no amount is entered

[tvolk131]

Fixes #257

[Copilot]

Pull Request Overview

This PR fixes issue #257 by disabling the "Generate Invoice" button when no amount is entered in the receive flow. The button becomes interactive only when the user has entered an amount value.

• Conditionally adds the on_press handler to the generate invoice button based on amount input
• Updates button styling to show disabled state with gray text color for both regular and small buttons

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
harbor-ui/src/routes/receive.rs	Conditionally enables the generate invoice button only when amount is entered
harbor-ui/src/components/button.rs	Updates button styling to display gray text for disabled buttons

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[Copilot]

The condition only checks if the string is not empty, but doesn't validate if it contains a valid amount. An empty string, whitespace-only string, or invalid input like 'abc' would be treated differently. Consider checking for a valid parsed amount instead of just non-empty string.

Suggested change

	if !harbor.receive_amount_str.is_empty() {
	if harbor
	.receive_amount_str
	.trim()
	.parse::<u64>()
	.map_or(false, |amt| amt > 0)
	{