Add ValidatePDF feature with API, Swagger, and tests

Implemented the ValidatePDF feature end-to-end:
- Added `/api/v1/documents/validate` Minimal API endpoint.
- Introduced centralized ExceptionHandlingMiddleware.
- Configured Swagger with `AddSwaggerDocumentation` extension.
- Enabled XML comments in `DocumentOperator.API.csproj`.
- Updated DTOs with XML comments and added `FileSizeMB`.
- Added integration tests for the ValidatePDF endpoint (3 tests).
- Registered infrastructure services (e.g., `IPdfProcessor`).
- Refactored `Program.cs` to include middleware and endpoints.
- Updated PHASENPLAN.md and ROADMAP.md to reflect progress.
- Cleaned up code and made `Program` accessible for tests.

DocumentOperator.API/Program.cs

@@ -1,5 +1,10 @@
 using Serilog;
 using DocumentOperator.Infrastructure.Configuration;
+using DocumentOperator.Application;
+using DocumentOperator.Infrastructure;
+using DocumentOperator.API.Middleware;
+using DocumentOperator.API.Endpoints.v1;
+using DocumentOperator.API.Configuration;
 
 var builder = WebApplication.CreateBuilder(args);
 
@@ -31,11 +36,13 @@ try
         builder.Configuration.GetSection(ApiKeySettings.SectionName));
 
     // ========================================
-    // 3. Services
+    // 3. Services (Clean Architecture Layers)
     // ========================================
-    builder.Services.AddControllers();
+    builder.Services.AddApplication();      // Application Layer (MediatR, FluentValidation, Behaviors)
+    builder.Services.AddInfrastructure();   // Infrastructure Layer (DevExpress, Services)
+
     builder.Services.AddEndpointsApiExplorer();
-    builder.Services.AddSwaggerGen();
+    builder.Services.AddSwaggerDocumentation();
 
     // ========================================
     // 4. Build App
@@ -43,8 +50,12 @@ try
     var app = builder.Build();
 
     // ========================================
-    // 5. Middleware Pipeline
+    // 5. Middleware Pipeline (Order matters!)
     // ========================================
+
+    // Exception Handling FIRST (catches all exceptions from subsequent middleware)
+    app.UseMiddleware<ExceptionHandlingMiddleware>();
+
     if (app.Environment.IsDevelopment())
     {
         app.UseSwagger();
@@ -54,8 +65,11 @@ try
     app.UseSerilogRequestLogging(); // Log HTTP Requests
 
     app.UseHttpsRedirection();
-    app.UseAuthorization();
-    app.MapControllers();
+
+    // ========================================
+    // 6. Endpoints (Minimal API)
+    // ========================================
+    app.MapDocumentEndpoints(); // POST /api/v1/documents/validate
 
     Log.Information("DocumentOperator API started successfully");
 
@@ -69,4 +83,7 @@ catch (Exception ex)
 finally
 {
     Log.CloseAndFlush();
-}
+}
+
+// Make Program class accessible for Integration Tests
+public partial class Program { }