## Summary
- Lazy auth-flow routes (`SignInUp`, `Invite`, `ResetPassword`,
`CreateWorkspace`, `CreateProfile`, `SyncEmails`, `InviteTeam`,
`PlanRequired`, `PlanRequiredSuccess`, `BookCallDecision`, `BookCall`)
render through `<Outlet/>` inside `<AuthModal>`. Their `LazyRoute`
`<Suspense>` fallback was the page-level `PageContentSkeletonLoader`, so
the two grey shimmer bars painted **inside the modal box** for a few
hundred ms while each chunk downloaded.
- `LazyRoute` now accepts an optional `fallback` prop (default
unchanged: the existing page skeleton). Every auth-modal route passes
`fallback={null}` so the modal stays empty until the lazy chunk resolves
instead of flashing the shimmer.
- `AuthModal`'s inner `StyledContent` gets a `min-height: 320px` so the
framer-motion `layout` animation doesn't rapidly resize the modal as
inner steps (loader → form → password → 2FA / workspace selection) swap.
The modal can still grow for taller steps; only the rapid jump is
removed.
## Why default-parameter syntax for `fallback`
`fallback ?? <LazyRouteFallback/>` would treat an explicit `null` as "no
value" and still render the default skeleton. Using a default parameter
(`fallback = <LazyRouteFallback/>`) preserves an explicit `null` because
defaults only kick in for `undefined`.
