Modify the no-status.js template in the RSVP block to allow guest users to initiate an RSVP flow.

Acceptance Criteria:
• Update the Login Modal to include a “RSVP as Guest” button/link.
• Clicking this closes the current modal and opens a new one (design can be basic for now).
• New modal includes:
• Three form-input blocks: one for Full Name, one for Email, one for notification opt-in checkbox
• A core/button block (or custom GatherPress variant) to represent the submission action
• Add setting at global/event levels for enabling open RSVP

Notes:
• This task is frontend-only: purely layout and block structure.
• Submission logic, validation, and backend flow will be implemented separately.