Add mobile UX optimization with toggleable deliveries overlay

- Add MobileDeliveriesListOpenNotifier provider for overlay state
- Create MobileMapWithOverlay component with slide-up animation
- Update routes_page.dart for responsive mobile/tablet/desktop layouts
- Mobile: full-screen map with FAB toggle for deliveries list
- Tablet/Desktop: maintain existing split-view layout

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

lib/providers/providers.dart

@@ -179,6 +179,19 @@ final collapseStateProvider = NotifierProvider<CollapseStateNotifier, bool>(() {
   return CollapseStateNotifier();
 });
 
+// Mobile deliveries list toggle state notifier for mobile overlay
+class MobileDeliveriesListOpenNotifier extends Notifier<bool> {
+  @override
+  bool build() => false; // Default: closed
+
+  void toggle() => state = !state;
+  void setOpen(bool open) => state = open;
+}
+
+final mobileDeliveriesListOpenProvider = NotifierProvider<MobileDeliveriesListOpenNotifier, bool>(() {
+  return MobileDeliveriesListOpenNotifier();
+});
+
 class _EmptyQuery implements Serializable {
   @override
   Map<String, Object?> toJson() => {};