* fix: defer email validation to after first blur on signup form
Change react-hook-form validation mode from "onChange" to "onTouched"
so that the "Invalid email" error only appears after the user has
interacted with the field and moved away, not on every keystroke.
Password strength hints still update in real-time since onTouched
validates on change after the field has been touched (blurred once).
Fixes#19163
* test: add unit tests for signup email validation mode
Verify the onTouched form validation behavior:
- No error shown while user is typing
- Error appears only after blur with invalid email
- No error for valid email after blur
- Revalidation on each keystroke after first blur
* remove eslint comment
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Co-authored-by: Dhairyashil <dhairyashil10101010@gmail.com>
