Build an OTP input with resend timer

• Renders N single-digit inputs (default 6); only digits 0 to 9 are accepted
• Typing a digit fills the box and moves focus to the next one
• Backspace on an empty box clears and focuses the previous box; Backspace on a filled box clears it
• Pasting a full code anywhere fills all boxes from the clipboard text (non-digits stripped, extra characters ignored)
• Arrow Left and Right move between boxes; the first box is focused on mount
• Calls onComplete(code) exactly once when all boxes are filled
• A resend button is disabled with a visible countdown (for example 30 seconds) and re-enables at zero; clicking it restarts the timer and clears the boxes

Only after every requirement works.

• autocomplete="one-time-code" and inputMode="numeric" so mobile keyboards and SMS autofill work
• Show an error state with a shake and clear on the next input
• Announce the countdown and errors to screen readers with aria-live