feat: implement filtered book navigation and improve author sorting

- Sort authors by surname (last word in name) instead of first name
- Create FilteredLibraryItemsPage to display books filtered by author/genre/series
- Add navigation from authors/genres/series pages to filtered book lists
- Use AuthorFilter, GenreFilter, and SeriesFilter from shelfsdk
- Add libraryFiltered route with filter parameter support

Users can now:
- Browse authors sorted by surname
- Tap on an author to see all their books
- Tap on a genre to see all books in that genre
- Tap on a series to see all books in that series

lib/features/library_browser/view/filtered_library_items_page.dart

@@ -0,0 +1,208 @@
+import 'package:cached_network_image/cached_network_image.dart';
+import 'package:flutter/material.dart';
+import 'package:go_router/go_router.dart';
+import 'package:hooks_riverpod/hooks_riverpod.dart';
+import 'package:shelfsdk/audiobookshelf_api.dart';
+import 'package:vaani/api/api_provider.dart';
+import 'package:vaani/api/library_provider.dart';
+import 'package:vaani/router/router.dart';
+import 'package:vaani/settings/api_settings_provider.dart';
+
+/// Page that displays library items filtered by author, genre, or series
+class FilteredLibraryItemsPage extends HookConsumerWidget {
+  const FilteredLibraryItemsPage({
+    super.key,
+    required this.filter,
+    required this.title,
+  });
+
+  final Filter filter;
+  final String title;
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final api = ref.watch(authenticatedApiProvider);
+    final currentLibraryAsync = ref.watch(currentLibraryProvider);
+
+    return Scaffold(
+      appBar: AppBar(
+        title: Text(title),
+      ),
+      body: currentLibraryAsync.when(
+        data: (library) {
+          if (library == null) {
+            return const Center(
+              child: Text('No library selected'),
+            );
+          }
+
+          return FutureBuilder<GetLibrarysItemsResponse?>(
+            future: api.libraries.getItems(
+              libraryId: library.id,
+              parameters: GetLibrarysItemsReqParams(
+                filter: filter,
+                sort: 'media.metadata.title',
+                limit: 100,
+              ),
+            ),
+            builder: (context, snapshot) {
+              if (snapshot.connectionState == ConnectionState.waiting) {
+                return const Center(
+                  child: CircularProgressIndicator(),
+                );
+              }
+
+              if (snapshot.hasError) {
+                return Center(
+                  child: Column(
+                    mainAxisAlignment: MainAxisAlignment.center,
+                    children: [
+                      const Icon(Icons.error_outline,
+                          size: 48, color: Colors.red),
+                      const SizedBox(height: 16),
+                      Text('Error: ${snapshot.error}'),
+                    ],
+                  ),
+                );
+              }
+
+              final response = snapshot.data;
+              if (response == null || response.results.isEmpty) {
+                return const Center(
+                  child: Text('No items found'),
+                );
+              }
+
+              return ListView.builder(
+                padding: const EdgeInsets.symmetric(vertical: 8),
+                itemCount: response.results.length,
+                itemBuilder: (context, index) {
+                  final item = response.results[index];
+                  return LibraryItemListTile(item: item);
+                },
+              );
+            },
+          );
+        },
+        loading: () => const Center(
+          child: CircularProgressIndicator(),
+        ),
+        error: (error, stack) => Center(
+          child: Text('Error: $error'),
+        ),
+      ),
+    );
+  }
+}
+
+class LibraryItemListTile extends ConsumerWidget {
+  const LibraryItemListTile({
+    super.key,
+    required this.item,
+  });
+
+  final LibraryItem item;
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final apiSettings = ref.watch(apiSettingsProvider);
+    final media = item.media;
+
+    // Extract book info
+    String title = '';
+    String? subtitle;
+    String? authorName;
+
+    if (media is MediaBook) {
+      final metadata = media.metadata;
+      if (metadata is BookMetadata) {
+        title = metadata.title ?? 'Unknown';
+        subtitle = metadata.subtitle;
+        authorName = metadata.authorName;
+      } else if (metadata is BookMetadataMinified) {
+        title = metadata.title ?? 'Unknown';
+        authorName = metadata.authorName;
+      } else if (metadata is BookMetadataExpanded) {
+        title = metadata.title ?? 'Unknown';
+        subtitle = metadata.subtitle;
+        final authors = metadata.authors;
+        if (authors != null && authors.isNotEmpty) {
+          authorName = authors.map((a) => a.name).join(', ');
+        }
+      }
+    }
+
+    final imageUrl = apiSettings.activeServer != null
+        ? '${apiSettings.activeServer!.serverUrl}/api/items/${item.id}/cover'
+        : null;
+
+    return Card(
+      margin: const EdgeInsets.symmetric(horizontal: 16, vertical: 4),
+      child: ListTile(
+        leading: imageUrl != null
+            ? ClipRRect(
+                borderRadius: BorderRadius.circular(4),
+                child: CachedNetworkImage(
+                  imageUrl: imageUrl,
+                  width: 48,
+                  height: 48,
+                  fit: BoxFit.cover,
+                  httpHeaders: {
+                    if (apiSettings.activeUser?.authToken != null)
+                      'Authorization':
+                          'Bearer ${apiSettings.activeUser!.authToken}',
+                  },
+                  placeholder: (context, url) => Container(
+                    width: 48,
+                    height: 48,
+                    color: Theme.of(context).colorScheme.surfaceContainerHighest,
+                    child: const Icon(Icons.book, size: 24),
+                  ),
+                  errorWidget: (context, url, error) => Container(
+                    width: 48,
+                    height: 48,
+                    color: Theme.of(context).colorScheme.surfaceContainerHighest,
+                    child: const Icon(Icons.book, size: 24),
+                  ),
+                ),
+              )
+            : Container(
+                width: 48,
+                height: 48,
+                decoration: BoxDecoration(
+                  color: Theme.of(context).colorScheme.surfaceContainerHighest,
+                  borderRadius: BorderRadius.circular(4),
+                ),
+                child: const Icon(Icons.book, size: 24),
+              ),
+        title: Text(
+          title,
+          style: Theme.of(context).textTheme.titleMedium,
+          maxLines: 2,
+          overflow: TextOverflow.ellipsis,
+        ),
+        subtitle: Column(
+          crossAxisAlignment: CrossAxisAlignment.start,
+          children: [
+            if (authorName != null) Text(authorName),
+            if (subtitle != null)
+              Text(
+                subtitle,
+                style: Theme.of(context).textTheme.bodySmall,
+                maxLines: 1,
+                overflow: TextOverflow.ellipsis,
+              ),
+          ],
+        ),
+        trailing: const Icon(Icons.chevron_right),
+        onTap: () {
+          // Navigate to item detail page
+          context.goNamed(
+            Routes.you.name,
+            pathParameters: {'libraryItemId': item.id},
+          );
+        },
+      ),
+    );
+  }
+}

lib/features/library_browser/view/library_authors_page.dart

@@ -1,9 +1,11 @@
 import 'package:cached_network_image/cached_network_image.dart';
 import 'package:flutter/material.dart';
+import 'package:go_router/go_router.dart';
 import 'package:hooks_riverpod/hooks_riverpod.dart';
 import 'package:shelfsdk/audiobookshelf_api.dart';
 import 'package:vaani/api/api_provider.dart';
 import 'package:vaani/api/library_browser_provider.dart';
+import 'package:vaani/router/router.dart';
 import 'package:vaani/settings/api_settings_provider.dart';
 
 class LibraryAuthorsPage extends HookConsumerWidget {
@@ -25,9 +27,13 @@ class LibraryAuthorsPage extends HookConsumerWidget {
             );
           }
 
-          // Sort authors alphabetically by name
+          // Sort authors alphabetically by surname (last word in name)
           final sortedAuthors = List<Author>.from(authors)
-            ..sort((a, b) => a.name.toLowerCase().compareTo(b.name.toLowerCase()));
+            ..sort((a, b) {
+              final aSurname = a.name.split(' ').last.toLowerCase();
+              final bSurname = b.name.split(' ').last.toLowerCase();
+              return aSurname.compareTo(bSurname);
+            });
 
           return GridView.builder(
             padding: const EdgeInsets.all(16),
@@ -98,12 +104,13 @@ class AuthorCard extends HookConsumerWidget {
       clipBehavior: Clip.antiAlias,
       child: InkWell(
         onTap: () {
-          // TODO: Navigate to author detail page
-          ScaffoldMessenger.of(context).showSnackBar(
-            SnackBar(
-              content: Text('Tapped on ${author.name}'),
-              duration: const Duration(seconds: 1),
-            ),
+          // Navigate to filtered items page with author filter
+          context.goNamed(
+            Routes.libraryFiltered.name,
+            extra: {
+              'filter': AuthorFilter(author.id),
+              'title': author.name,
+            },
           );
         },
         child: Column(

lib/features/library_browser/view/library_genres_page.dart

@@ -1,6 +1,9 @@
 import 'package:flutter/material.dart';
+import 'package:go_router/go_router.dart';
 import 'package:hooks_riverpod/hooks_riverpod.dart';
+import 'package:shelfsdk/audiobookshelf_api.dart';
 import 'package:vaani/api/library_browser_provider.dart';
+import 'package:vaani/router/router.dart';
 
 class LibraryGenresPage extends HookConsumerWidget {
   const LibraryGenresPage({super.key});
@@ -82,12 +85,13 @@ class GenreListTile extends StatelessWidget {
         ),
         trailing: const Icon(Icons.chevron_right),
         onTap: () {
-          // TODO: Navigate to books in this genre
-          ScaffoldMessenger.of(context).showSnackBar(
-            SnackBar(
-              content: Text('Tapped on $genre'),
-              duration: const Duration(seconds: 1),
-            ),
+          // Navigate to filtered items page with genre filter
+          context.goNamed(
+            Routes.libraryFiltered.name,
+            extra: {
+              'filter': GenreFilter(genre),
+              'title': genre,
+            },
           );
         },
       ),

lib/features/library_browser/view/library_series_page.dart

@@ -1,6 +1,9 @@
 import 'package:flutter/material.dart';
+import 'package:go_router/go_router.dart';
 import 'package:hooks_riverpod/hooks_riverpod.dart';
+import 'package:shelfsdk/audiobookshelf_api.dart';
 import 'package:vaani/api/library_browser_provider.dart';
+import 'package:vaani/router/router.dart';
 
 class LibrarySeriesPage extends HookConsumerWidget {
   const LibrarySeriesPage({super.key});
@@ -82,12 +85,13 @@ class SeriesListTile extends StatelessWidget {
             : null,
         trailing: const Icon(Icons.chevron_right),
         onTap: () {
-          // TODO: Navigate to series detail page
-          ScaffoldMessenger.of(context).showSnackBar(
-            SnackBar(
-              content: Text('Tapped on ${series.name}'),
-              duration: const Duration(seconds: 1),
-            ),
+          // Navigate to filtered items page with series filter
+          context.goNamed(
+            Routes.libraryFiltered.name,
+            extra: {
+              'filter': SeriesFilter(series.id),
+              'title': series.name,
+            },
           );
         },
       ),

lib/router/constants.dart

@@ -101,6 +101,12 @@ class Routes {
     parentRoute: libraryBrowser,
   );
 
+  static const libraryFiltered = _SimpleRoute(
+    pathName: 'filtered',
+    name: 'libraryFiltered',
+    parentRoute: libraryBrowser,
+  );
+
   // you page for the user
   static const you = _SimpleRoute(
     pathName: 'you',

lib/router/router.dart

@@ -4,6 +4,7 @@ import 'package:vaani/features/downloads/view/downloads_page.dart';
 import 'package:vaani/features/explore/view/explore_page.dart';
 import 'package:vaani/features/explore/view/search_result_page.dart';
 import 'package:vaani/features/item_viewer/view/library_item_page.dart';
+import 'package:vaani/features/library_browser/view/filtered_library_items_page.dart';
 import 'package:vaani/features/library_browser/view/library_authors_page.dart';
 import 'package:vaani/features/library_browser/view/library_browser_page.dart';
 import 'package:vaani/features/library_browser/view/library_genres_page.dart';
@@ -140,6 +141,31 @@ class MyAppRouter {
                         name: Routes.librarySeries.name,
                         pageBuilder: defaultPageBuilder(const LibrarySeriesPage()),
                       ),
+                      GoRoute(
+                        path: Routes.libraryFiltered.pathName,
+                        name: Routes.libraryFiltered.name,
+                        pageBuilder: (context, state) {
+                          final extra = state.extra as Map<String, dynamic>?;
+                          final filter = extra?['filter'] as Filter?;
+                          final title = extra?['title'] as String? ?? 'Filtered Items';
+                          if (filter == null) {
+                            return MaterialPage(
+                              child: Scaffold(
+                                appBar: AppBar(title: const Text('Error')),
+                                body: const Center(
+                                  child: Text('Invalid filter'),
+                                ),
+                              ),
+                            );
+                          }
+                          return MaterialPage(
+                            child: FilteredLibraryItemsPage(
+                              filter: filter,
+                              title: title,
+                            ),
+                          );
+                        },
+                      ),
                     ],
                   ),
                 ],