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.
MMD