Animate the Orders list out on sign out via the View Transitions API

Wraps the sign-out-triggered router.invalidate() in
document.startViewTransition() so the cleared order cards cross-fade
out (and the empty state fades in) instead of popping away instantly.
Each order card already carries its own view-transition-name (see
OrdersListView), so this reuses that per-card exit; the existing
::view-transition-group(*) timing in globals.scss applies automatically.

Falls back to a plain invalidate() where the API is unsupported, and
swallows rejection on the transition's ready/finished promises since
the browser can abort it in some states (e.g. a backgrounded tab) —
router.invalidate() still runs regardless.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/integrations/better-auth/header-user.tsx

@@ -153,7 +153,27 @@ const BetterAuthHeader = () => {
                   clearBasket()
                   void authClient.signOut({
                     fetchOptions: {
-                      onSuccess: () => void router.invalidate(),
+                      onSuccess: () => {
+                        // Cross-fades the now-cleared Orders list out (and
+                        // the empty state in) instead of popping instantly —
+                        // each order card already carries its own
+                        // `view-transition-name` (see OrdersListView), so
+                        // this reuses that for a proper per-card exit.
+                        if ('startViewTransition' in document) {
+                          // Rejects if the browser can't actually run the
+                          // transition right now (e.g. the tab isn't
+                          // visible) — router.invalidate() still runs either
+                          // way, so there's nothing to handle beyond not
+                          // leaving this as an unhandled rejection.
+                          const transition = document.startViewTransition(() =>
+                            router.invalidate(),
+                          )
+                          transition.ready.catch(() => {})
+                          transition.finished.catch(() => {})
+                        } else {
+                          void router.invalidate()
+                        }
+                      },
                     },
                   })
                 }}