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/components/TitleSync.tsx

@@ -0,0 +1,42 @@
+import { useEffect } from "react";
+import { useLocation } from "react-router-dom";
+import { menuSections, isItemActive } from "../ui/navData";
+
+/**
+ * Null-rendering helper that keeps the browser tab title in sync with the
+ * active navigation item. Scans menuSections in order (first match wins) via
+ * the same isItemActive logic the sidebar uses, so detail routes covered by
+ * matchPrefix (e.g. /offers/123) inherit their section item's label.
+ * No cleanup on unmount — the last title simply persists.
+ */
+// Labels reused across sections ("Záznam", "Moje historie", "Správa",
+// "Přehled") would produce identical tab titles — qualify those with their
+// section label so /attendance and /trips tabs stay distinguishable.
+const labelCounts = new Map<string, number>();
+for (const section of menuSections) {
+  for (const item of section.items) {
+    labelCounts.set(item.label, (labelCounts.get(item.label) ?? 0) + 1);
+  }
+}
+
+export default function TitleSync() {
+  const { pathname } = useLocation();
+
+  useEffect(() => {
+    for (const section of menuSections) {
+      const item = section.items.find((candidate) =>
+        isItemActive(candidate, pathname),
+      );
+      if (item) {
+        const ambiguous = (labelCounts.get(item.label) ?? 0) > 1;
+        document.title = ambiguous
+          ? `${item.label} – ${section.label} · BOHA`
+          : `${item.label} · BOHA`;
+        return;
+      }
+    }
+    document.title = "BOHA Admin";
+  }, [pathname]);
+
+  return null;
+}