Fix Microsoft SSO sign-up with profile photo

New users signing in through Microsoft or Azure AD SSO could fail to be created when their account had a profile photo, because Microsoft sends the photo as inline image data that exceeded an internal limit on the avatar field.

• Fixed account creation for Microsoft and Azure AD SSO users who have a profile photo
• Improved handling of inline profile photos so they no longer block sign-up
• Added a fallback to initials when no uploaded avatar is set