Merge main_v2 mobile UI into production, restore mobile bottom tab bar

Merges main_v2 a110741 (mobile UI optimizations) into production and
reinstates the mobile bottom navigation that f0e4243 had removed.

Conflicts in DashboardPage, QuoteCard and InventoryPage resolved in
favour of main_v2's mobile-first markup, keeping production's newer
design system (Button variant="primary" on InventoryPage).

f0e4243's removal was reverted in effect: MobileTabBar is restored and
remounted in App.tsx, and PageLayout regains max-md:pb-24 clearance so
content is not hidden behind the fixed bar.

frontend/src/App.tsx

@@ -3,6 +3,7 @@ import { Navigate, Route, Routes } from "react-router-dom";
 import { useAuthStore } from "./store/auth";
 import { ErrorBoundary } from "./components/ErrorBoundary";
 import { RequirePmProjects } from "./components/RequirePmProjects";
+import { MobileTabBar } from "./components/layout/MobileTabBar";
 
 // هر صفحه با React.lazy لود می‌شود (code splitting)
 const DashboardPage = lazy(() =>
@@ -209,6 +210,7 @@ export default function App() {
         <Route path="*" element={<Navigate to="/" replace />} />
         </Routes>
       </Suspense>
+      <MobileTabBar />
     </ErrorBoundary>
   );
 }