Implement light minimalistic tech redesign with Material 3

Complete transformation from dark to light theme with a professional,
tech-forward design system featuring:

- Material 3 theming with cyan-based color palette (#0891B2 primary)
- Inter font family integration via Google Fonts
- Comprehensive theme system (colors, spacing, typography, shadows)
- Responsive component redesign across all screens
- Enhanced UX with hover animations, Hero transitions, and shimmer loading
- Accessibility features (reduced motion support, high contrast)
- Clean architecture with zero hardcoded values

Theme System:
- Created app_colors.dart with semantic color constants
- Created app_spacing.dart with 8px base spacing scale
- Created app_theme.dart with complete Material 3 configuration
- Added shimmer_loading.dart for image loading states

UI Components Updated:
- Book cards with hover effects and Hero animations
- Bottom navigation with refined styling
- All screens migrated to theme-based colors and typography
- Forms and inputs using consistent design system

Documentation:
- Added REDESIGN_SUMMARY.md with complete implementation overview
- Added IMPLEMENTATION_CHECKLIST.md with detailed task completion status

All components now use centralized theme with no hardcoded values,
ensuring consistency and easy future customization.

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

books_flutter/lib/models/models.dart

@@ -0,0 +1,36 @@
+import 'package:flutter/material.dart';
+
+typedef Book = ({
+  String id,
+  String title,
+  String author,
+  String genre,
+  String annotation,
+  String? coverUrl,
+  int? pages,
+  String? language,
+  int? publishedYear,
+  double? rating,
+  String status,
+  double? progress,
+  bool isFavorite,
+});
+
+typedef Category = ({
+  String id,
+  String name,
+  int count,
+  IconData icon,
+  Color iconColor,
+  Color backgroundColor,
+});
+
+enum AppScreen {
+  library,
+  categories,
+  wishlist,
+  settings,
+  details,
+  addBook,
+  scanner,
+}