Improve exception handling with ProblemDetails responses

ExceptionHandlingMiddleware now returns structured ProblemDetails
responses for errors, including specific handling for
InvalidOperationException (400 Bad Request) and general exceptions
(500 Internal Server Error). Responses use "application/problem+json"
content type and include trace IDs. ProblemDetails support is also
registered in Program.cs.

DbFirst.API/Program.cs

@@ -13,6 +13,7 @@ var builder = WebApplication.CreateBuilder(args);
 builder.Services.AddControllers();
 builder.Services.AddEndpointsApiExplorer();
 builder.Services.AddSwaggerGen();
+builder.Services.AddProblemDetails();
 
 // TODO: allow listed origins configured in appsettings.json
 // In any case, dont let them to free to use without cors. if there is no origin specified, block all.