feat: implement library view with Authors, Genres, and Series browsing

This commit implements a comprehensive library browsing feature:

- Add LibraryBrowserProvider with providers for authors, genres, and series data
- Create LibraryAuthorsPage with grid view of authors including images and book counts
- Create LibraryGenresPage with list view of all genres
- Create LibrarySeriesPage with list view of series and book counts
- Update LibraryBrowserPage navigation to route to the new views
- Add routes for /browser/authors, /browser/genres, and /browser/series
- Replace "Not Implemented" toasts with functional navigation

The implementation uses the Audiobookshelf API via shelfsdk to fetch:
- Authors list with metadata (getAuthors)
- Genres from library filter data (getFilterData)
- Series with pagination support (getSeries)

All views follow Material Design 3 patterns and include proper loading/error states.

lib/features/library_browser/view/library_genres_page.dart

@@ -0,0 +1,96 @@
+import 'package:flutter/material.dart';
+import 'package:hooks_riverpod/hooks_riverpod.dart';
+import 'package:vaani/api/library_browser_provider.dart';
+
+class LibraryGenresPage extends HookConsumerWidget {
+  const LibraryGenresPage({super.key});
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final genresAsync = ref.watch(libraryGenresProvider);
+
+    return Scaffold(
+      appBar: AppBar(
+        title: const Text('Genres'),
+      ),
+      body: genresAsync.when(
+        data: (genres) {
+          if (genres.isEmpty) {
+            return const Center(
+              child: Text('No genres found'),
+            );
+          }
+
+          // Sort genres alphabetically
+          final sortedGenres = List<String>.from(genres)..sort();
+
+          return ListView.builder(
+            padding: const EdgeInsets.symmetric(vertical: 8),
+            itemCount: sortedGenres.length,
+            itemBuilder: (context, index) {
+              final genre = sortedGenres[index];
+              return GenreListTile(genre: genre);
+            },
+          );
+        },
+        loading: () => const Center(
+          child: CircularProgressIndicator(),
+        ),
+        error: (error, stack) => Center(
+          child: Column(
+            mainAxisAlignment: MainAxisAlignment.center,
+            children: [
+              const Icon(Icons.error_outline, size: 48, color: Colors.red),
+              const SizedBox(height: 16),
+              Text('Error loading genres: $error'),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}
+
+class GenreListTile extends StatelessWidget {
+  const GenreListTile({
+    super.key,
+    required this.genre,
+  });
+
+  final String genre;
+
+  @override
+  Widget build(BuildContext context) {
+    return Card(
+      margin: const EdgeInsets.symmetric(horizontal: 16, vertical: 4),
+      child: ListTile(
+        leading: Container(
+          width: 48,
+          height: 48,
+          decoration: BoxDecoration(
+            color: Theme.of(context).colorScheme.primaryContainer,
+            borderRadius: BorderRadius.circular(8),
+          ),
+          child: Icon(
+            Icons.category,
+            color: Theme.of(context).colorScheme.onPrimaryContainer,
+          ),
+        ),
+        title: Text(
+          genre,
+          style: Theme.of(context).textTheme.titleMedium,
+        ),
+        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),
+            ),
+          );
+        },
+      ),
+    );
+  }
+}