feat(api): Enable conditional Swagger/Scalar in production

Program.cs changes:
- Add Scalar.AspNetCore using
- Register SwaggerSettings with Options Pattern
- Pass IConfiguration to AddSwaggerDocumentation()
- Conditional middleware: Development OR EnableInProduction=true
- Add Swagger UI with custom endpoint configuration
- Add Scalar UI at /scalar/v1 (DeepSpace theme, C# HttpClient target)

Access URLs:
- Swagger UI: https://localhost:7186/swagger
- Scalar UI: https://localhost:7186/scalar/v1
- Serilog UI: https://localhost:7186/serilog-ui

Production behavior: Swagger+Scalar enabled by default (configurable)

DocumentOperator.API/Program.cs

@@ -2,6 +2,7 @@ using Serilog;
 using Serilog.Ui.Core.Extensions;
 using Serilog.Ui.SqliteDataProvider.Extensions;
 using Serilog.Ui.Web.Extensions;
+using Scalar.AspNetCore;
 using DocumentOperator.Infrastructure.Configuration;
 using DocumentOperator.Application;
 using DocumentOperator.Infrastructure;
@@ -37,6 +38,9 @@ try
     builder.Services.Configure<ApiKeySettings>(
         builder.Configuration.GetSection(ApiKeySettings.SectionName));
 
+    builder.Services.Configure<SwaggerSettings>(
+        builder.Configuration.GetSection(SwaggerSettings.SectionName));
+
     // ========================================
     // 3. Services (Clean Architecture Layers)
     // ========================================
@@ -45,7 +49,7 @@ try
 
     builder.Services.AddControllers();      // Controllers (Controller-based API)
     builder.Services.AddEndpointsApiExplorer();
-    builder.Services.AddSwaggerDocumentation();
+    builder.Services.AddSwaggerDocumentation(builder.Configuration);
 
     // ========================================
     // 4. Serilog.UI Configuration
@@ -75,10 +79,32 @@ try
     // Exception Handling FIRST (catches all exceptions from subsequent middleware)
     app.UseMiddleware<ExceptionHandlingMiddleware>();
 
-    if (app.Environment.IsDevelopment())
+    // ========================================
+    // Swagger/OpenAPI (Conditional based on settings)
+    // ========================================
+    var swaggerSettings = builder.Configuration.GetSection(SwaggerSettings.SectionName).Get<SwaggerSettings>()
+        ?? new SwaggerSettings();
+
+    if (app.Environment.IsDevelopment() || swaggerSettings.EnableInProduction)
     {
         app.UseSwagger();
-        app.UseSwaggerUI();
+        
+        // Swagger UI (classic)
+        app.UseSwaggerUI(options =>
+        {
+            options.SwaggerEndpoint($"/swagger/{swaggerSettings.Version}/swagger.json", 
+                $"{swaggerSettings.Title} {swaggerSettings.Version}");
+            options.RoutePrefix = "swagger"; // /swagger
+        });
+
+        // Scalar UI (modern alternative)
+        app.MapScalarApiReference(options =>
+        {
+            options
+                .WithTitle(swaggerSettings.Title)
+                .WithTheme(ScalarTheme.DeepSpace)
+                .WithDefaultHttpClient(ScalarTarget.CSharp, ScalarClient.HttpClient);
+        });
     }
 
     app.UseSerilogRequestLogging(); // Log HTTP Requests