feat(mui): consistent staggered page entrance across all 43 route pages

Adopt the PageEnter wrapper as every page's outermost render element and remove the ad-hoc per-page entrance motion.div wrappers. Every page now enters the same way — all top-level sections rise+fade in, staggered — so nothing appears instantly and the motion is identical app-wide. Presentation-only: no data/logic/hooks/invalidate/permissions touched. Embedded sub-tabs (CompanySettings, ReceivedInvoices), Login (auth shell) and the dev UiKit are intentionally excluded. Gates: tsc -b --noEmit=0, build=0, vitest 152/152.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/admin/pages/AttendanceBalances.tsx

@@ -25,6 +25,7 @@ import {
   Select,
   StatusChip,
   PageHeader,
+  PageEnter,
   EmptyState,
   LoadingState,
   ProgressBar,
@@ -392,7 +393,7 @@ export default function AttendanceBalances() {
   ];
 
   return (
-    <Box>
+    <PageEnter>
       <PageHeader
         title="Správa bilancí"
         actions={
@@ -815,6 +816,6 @@ export default function AttendanceBalances() {
         confirmVariant="danger"
         loading={resetMutation.isPending}
       />
-    </Box>
+    </PageEnter>
   );
 }