More reliable participant onboarding and redirects

Smarter auto-redirect Auto-redirects after interview completion now use the same URL handling as manual clicks for consistency, including search parameters and environment swaps.

• Welcome wizard timing The welcome screen now waits for participant info to be ready before processing, so fields no longer go missing on completion.
• Broader compatibility for participant data: common alternative field names for first name, last name, company, company size, and email consent are now recognized automatically.