chore: weekly sync — bump @btst/stack to >=2.8.1, fix better-auth 1.5.x compat, bump to v1.2.4#5

cursor[bot] wants to merge 2 commits intomainbetter-stack-ai/better-auth-ui:mainfrom

cursor/upstream-better-auth-ui-sync-4e0bbetter-stack-ai/better-auth-ui:cursor/upstream-better-auth-ui-sync-4e0bCopy head branch name to clipboard