refactor: create separate BLoCs for each screen with comprehensive tests

- Created 8 separate BLoCs (Home, Library, BookDetails, AddBook, Scanner, Categories, Wishlist, Settings)
- Each BLoC has its own event, state, and bloc files
- Added 70 comprehensive tests covering all BLoC functionality
- All tests passing (70/70)
- Fixed linting issues and updated deprecated APIs
- Improved code organization and maintainability

bookshelf_flutter/lib/screens/settings_screen.dart

@@ -0,0 +1,39 @@
+import 'package:flutter/material.dart';
+
+class SettingsScreen extends StatelessWidget {
+  const SettingsScreen({super.key});
+
+  @override
+  Widget build(BuildContext context) {
+    return Scaffold(
+      backgroundColor: const Color(0xFF112116),
+      body: Center(
+        child: Padding(
+          padding: const EdgeInsets.all(40),
+          child: Column(
+            mainAxisAlignment: MainAxisAlignment.center,
+            children: [
+              const Text(
+                'Настройки',
+                style: TextStyle(
+                  fontSize: 20,
+                  fontWeight: FontWeight.bold,
+                  color: Colors.white,
+                ),
+              ),
+              const SizedBox(height: 8),
+              Text(
+                'Персонализируйте ваше приложение.',
+                textAlign: TextAlign.center,
+                style: TextStyle(
+                  fontSize: 16,
+                  color: const Color(0xFF93C8A5),
+                ),
+              ),
+            ],
+          ),
+        ),
+      ),
+    );
+  }
+}