feat: Refactor routing and navigation structure with StatefulShellRoute

- Introduced a new function `_shellBranchIndexForPath` to determine the index of the shell branch based on the path.
- Replaced `ShellRoute` with `StatefulShellRoute.indexedStack` for better state management during navigation.
- Updated `AppShell` to handle navigation path changes and integrate with the new routing structure.
- Organized routes into `StatefulShellBranch` for better modularity and clarity.
- Enhanced admin panel functionality with improved alias management and UI updates.
- Added new methods in `ReceiptImportSessionNotifier` for managing selected items and edits more efficiently.
- Improved UI components in receipt import and admin panels for better performance and user experience.
- Added PageStorageKeys to various ListViews to maintain scroll positions across navigation.
- Documented performance goals and profiling strategies in a new PERFORMANCE.md file.

flutter/lib/features/recipes/presentation/recipes_screen.dart

@@ -38,6 +38,7 @@ class RecipesScreen extends ConsumerWidget {
 
             if (view.mode == RecipesViewMode.grid) {
               return GridView.builder(
+                key: PageStorageKey<String>('recipes-grid-${view.columns}'),
                 padding: const EdgeInsets.only(bottom: 88),
                 gridDelegate: SliverGridDelegateWithFixedCrossAxisCount(
                   crossAxisCount: view.columns,
@@ -55,6 +56,7 @@ class RecipesScreen extends ConsumerWidget {
               );
             } else {
               return ListView.builder(
+                key: const PageStorageKey<String>('recipes-list'),
                 padding: const EdgeInsets.only(bottom: 88),
                 itemCount: recipes.length,
                 itemBuilder: (context, index) {