second commit

lib/presentation/pos/providers/navigation_provider.dart

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+import 'package:flutter/material.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+
+/// The modules a cashier needs. Deliberately excludes analytics — this
+/// terminal is for billing, not back-office reporting.
+enum PosModule {
+  pos('Point of Sale', 'POS', Icons.point_of_sale_rounded, NavSection.billing),
+  customers('Customers', 'Customers', Icons.people_alt_rounded,
+      NavSection.billing),
+
+  productImport('Product Import', 'Product Import',
+      Icons.cloud_download_rounded, NavSection.catalogue),
+  promos('Promotions', 'Promo', Icons.sell_rounded, NavSection.catalogue),
+
+  events('Events', 'Events', Icons.sync_rounded, NavSection.session),
+  settings('Settings', 'Settings', Icons.settings_rounded, NavSection.session);
+
+  const PosModule(this.title, this.label, this.icon, this.section);
+
+  /// Long form, shown in the page header.
+  final String title;
+
+  /// Short form, shown in the sidebar.
+  final String label;
+
+  final IconData icon;
+  final NavSection section;
+}
+
+/// Groups the navigation into labelled blocks.
+enum NavSection {
+  billing('Billing'),
+  catalogue('Catalogue'),
+  session('Session');
+
+  const NavSection(this.label);
+
+  final String label;
+
+  List<PosModule> get modules =>
+      PosModule.values.where((m) => m.section == this).toList();
+}
+
+final activeModuleProvider = StateProvider<PosModule>((ref) => PosModule.pos);