feat(shell): scrollable status tabs, per-page tab titles, skip-to-content, Czech MUI locale

- Shared Tabs: variant=scrollable + auto scroll buttons — the 5 status-filter
  tabs no longer clip unreachable at ~360px (desktop rendering unchanged).
- TitleSync: browser tab shows the active page ('Faktury · BOHA'; ambiguous
  labels qualified with their section, e.g. 'Záznam – Docházka · BOHA');
  index.html fallback now 'BOHA Admin'.
- Skip-to-content link (visually hidden, visible on focus) + id/tabIndex on
  <main> — keyboard users skip the 248px sidebar.
- MUI csCZ locale merged into the theme (kills built-in English strings like
  'No options'); Czech noOptionsText on Customer/Supplier pickers.

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

src/admin/ui/CustomerPicker.tsx

@@ -57,6 +57,7 @@ export default function CustomerPicker({
       size="small"
       fullWidth
       autoHighlight
+      noOptionsText="Žádní zákazníci"
       renderOption={(props, c) => {
         const { key, ...rest } = props as typeof props & { key: string };
         return (