feat(better-auth): add patches for PR #245, reorganize #218

[ramonclaudio]

adds bun + npm patches for two open PRs against @convex-dev/better-auth@0.10.10.

PR #218 (merged, no new release yet) — cross-domain auth fixes:

• expires.toISOString() serialization in getSetCookie
• new Date(value.expires) comparison in getCookie
• getSessionData rewrite with null/empty/error handling
• null session clears cookies
• Boolean(session?.session) for isAuthenticated

patches rebuilt from the final merged commit (includes maintainer additions, excludes our reverted localCacheName change).

PR #245 (open) — widens better-auth peer dep from exact 1.4.9 to >=1.4.9 <1.5.0.

also renames the existing npm patch to -pr218 suffix for consistency with the new -pr245 patches.

all 4 patches verified — git apply --check (bun) and patch-package (npm) pass against a fresh @convex-dev/better-auth@0.10.10 install from the registry tarball.