Make partner onboarding image optional and sync to user

[marcusljf]

Updated the onboarding form to make the profile image optional for partners.

Enhanced onboarding logic to sync the partner image to the user account only when creating a new partner and the user has no existing projects or custom image. So if they have no Dub account already, the image added during onboarding is used as their account profile image as well.

Summary by CodeRabbit

• New Features

  • Profile image upload is now optional during partner onboarding.
  • Automatic image synchronization to user accounts for new partners.

• Improvements

  • Updated form label from "Full Name" to "Name."
  • Added clearer image requirements: square format, 2 MB maximum.
  • Enhanced image preview and validation handling.

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