feat(auth): add redirects.logout

[onmax]

Summary

• Add optional auth.redirects.logout.
• When configured, useUserSession().signOut() navigates there by default (unless onSuccess is provided).
• Expose the value in the DevTools config endpoint.

Tests

• pnpm lint
• pnpm typecheck
• pnpm test

[pkg-pr-new]

Open in StackBlitz

npm i https://pkg.pr.new/nuxt-modules/better-auth/@onmax/nuxt-better-auth@173

commit: f14bc2e