fix(blocks): prevent invalid date selection in calendar-26

[Raghuboi]

Prevents invalid date selection in calendar-26 block.

When user changes check-in date to be same or after the check-out date, the check-out date now clears automatically to prevent invalid ranges.

Fixes case where changing check-in date after setting check-out could create invalid date combinations.

Testing Scenario

• Set check-out date (e.g., June 5th)
• Change check-in date to after check-out (e.g., June 6th)
• Verify check-out date clears to "Select date"

[vercel]

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[github-actions]

Looks like this PR modifies files in apps/www, which is deprecated.

Consider applying the change to apps/v4 if relevant.