Add Swagger/OpenAPI support (development only)

Add Swashbuckle.AspNetCore (v6.6.2) to API project and register Swagger services (AddEndpointsApiExplorer, AddSwaggerGen). Enable UseSwagger/UseSwaggerUI only in Development to expose /swagger for API exploration without affecting production behavior. Update codexInfo.md to document the dev-only Swagger endpoint.

API/Program.cs

@@ -1,11 +1,19 @@
 var builder = WebApplication.CreateBuilder(args);
 
 builder.Services.AddControllers();
+builder.Services.AddEndpointsApiExplorer();
+builder.Services.AddSwaggerGen();
 
 var app = builder.Build();
 var webRootPath = app.Environment.WebRootPath ?? Path.Combine(app.Environment.ContentRootPath, "wwwroot");
 var indexFilePath = Path.Combine(webRootPath, "index.html");
 
+if (app.Environment.IsDevelopment())
+{
+    app.UseSwagger();
+    app.UseSwaggerUI();
+}
+
 app.UseDefaultFiles();
 app.UseStaticFiles();