Add comprehensive test suite infrastructure

- Create backend xUnit test project with Moq and FluentAssertions
- Add test utilities: TestDataFactory, MockHttpContext, TestUserClaims
- Create AuthControllerTests with comprehensive auth scenarios
- Install Jest and React Testing Library for frontend
- Configure jest.config.ts and jest.setup.ts with Next.js support
- Add test scripts to package.json

backend/backend.Tests/Utilities/MockHttpContext.cs

@@ -0,0 +1,38 @@
+using System.Security.Claims;
+using Microsoft.AspNetCore.Http;
+
+namespace backend.Tests.Utilities;
+
+public static class MockHttpContext
+{
+    public static HttpContext Create(
+        string userId = "test-user-id",
+        string email = "test@example.com",
+        string role = "Participant",
+        bool isAuthenticated = true)
+    {
+        var claims = new List<Claim>();
+        
+        if (isAuthenticated)
+        {
+            claims.Add(new Claim(ClaimTypes.NameIdentifier, userId));
+            claims.Add(new Claim(ClaimTypes.Email, email));
+            claims.Add(new Claim(ClaimTypes.Role, role));
+        }
+
+        var identity = new ClaimsIdentity(claims, isAuthenticated ? "TestAuthType" : null);
+        var principal = new ClaimsPrincipal(identity);
+
+        var httpContext = new DefaultHttpContext
+        {
+            User = principal
+        };
+
+        return httpContext;
+    }
+
+    public static HttpContext CreateAnonymous()
+    {
+        return Create(isAuthenticated: false);
+    }
+}