Default UI: Add Inline Regwall

🔍 Problem Statement
As a digital publisher, I experience readers accessing content without identifying themselves, which prevents audience growth, first-party data collection, and personalized re-engagement.

💡 User Story
As a site visitor, I want to register with my email before accessing full articles, so that I can read content and receive relevant updates.
As a publisher, I want an inline registration wall that collects user identity before content access, so that I can build a first-party audience.

🎯 Definition of Done
- Given a non-authenticated user on a metered article, when the regwall triggers, then an inline registration form is displayed within the content (not a modal overlay).
- This change impacts the JS-SDK (new regwall component), ReactJS Elements (inline regwall UI), and API (registration endpoint).
- Limitations: v1 supports email + password only; social login is out of scope.

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Problem Statement As a digital publisher, I experience a lack of user identity capture before content access, which results in missed opportunities to build a direct audience and personalize experiences. User Story As a site visitor, I want to register with my name, email, password before accessing articles, so that I can read content and receive future updates. As a publisher, I want to present an inline registration wall, so that users are minimally interrupted while still required to identify themselves. Definition of Done (DoD) A feature is done when: If displayPaywall is true, user is not authenticated, and type of paywall=inline, then display inline regwall that covers any part of the page wrapped with the following DIV ID=pelcro-inline-regwall By default, email and password are required, but if enableNameFieldsInRegister is true in uiSettings , then name will be added Title and subtitle of the inline regwall must be retrieved from the paywall registration title and subtitle fields Primary and secondary colors of the regwall can be updated from the Pelcro platform