Add LittleShop.Client SDK library with complete API wrapper

Features:
- Complete .NET client SDK for LittleShop API
- JWT authentication with automatic token management
- Catalog service for products and categories
- Order service with payment creation
- Retry policies using Polly for resilience
- Error handling middleware
- Dependency injection support
- Comprehensive documentation and examples

SDK Components:
- Authentication service with token refresh
- Strongly-typed models for all API responses
- HTTP handlers for retry and error handling
- Extension methods for easy DI registration
- Example console application demonstrating usage

Test Updates:
- Fixed test compilation errors
- Updated test data builders for new models
- Corrected service constructor dependencies
- Fixed enum value changes (PaymentStatus, OrderStatus)

Documentation:
- Complete project README with features and usage
- Client SDK README with detailed examples
- API endpoint documentation
- Security considerations
- Deployment guidelines

Generated with Claude Code

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

LittleShop.Client/Configuration/LittleShopClientOptions.cs

@@ -0,0 +1,10 @@
+namespace LittleShop.Client.Configuration;
+
+public class LittleShopClientOptions
+{
+    public string BaseUrl { get; set; } = "https://localhost:5001";
+    public int TimeoutSeconds { get; set; } = 30;
+    public int MaxRetryAttempts { get; set; } = 3;
+    public bool EnableLogging { get; set; } = true;
+    public string? ApiKey { get; set; }
+}