Redirect root URL to Swagger UI; add required usings

Added several using directives to Program.cs for new dependencies. Updated HTTP pipeline to redirect requests from "/" to "/swagger" when Swagger is enabled, improving developer experience by automatically showing the API documentation.

src/ReC.API/Program.cs

@@ -1,3 +1,4 @@
+using Microsoft.AspNetCore.Rewrite;
 using Microsoft.EntityFrameworkCore;
 using NLog;
 using NLog.Web;
@@ -67,6 +68,9 @@ try
     {
         app.UseSwagger();
         app.UseSwaggerUI();
+
+        var rewriteOptions = new RewriteOptions().AddRedirect("^$", "swagger");
+        app.UseRewriter(rewriteOptions);
     }
 
     app.UseHttpsRedirection();