Redesigned sign-in and sign-up with split-screen layout

Split-screen auth pages with benefits panel and unified nav — Sign-in and sign-up pages were redesigned into a split-screen layout that places the authentication form alongside a short benefits panel. A new AuthPageNav component was added to the top of both pages, providing a persistent brand link, theme toggle, and the opposite action (Sign in / Sign up).

Added a shared AuthPageNav to auth pages with BrandLogo, theme toggle, and a clear opposite-action link.auth

Updated sign-in and sign-up to a two-column layout showing the auth form alongside concise product benefits (connect a GitHub repo, instant changelog generation, editorial workflow, hosted changelog).frontend
Refined Clerk form appearance and layout for improved readability, clearer CTAs, and consistent styling across auth pages.frontend
Added friendly, action-oriented copy and links on both pages to make it easier to switch between signing in and signing up.frontend