Fix blazor.web.js 404: move App.razor and Routes.razor to Host project

Root cause: App.razor was in CentralUI (Microsoft.NET.Sdk.Razor RCL) but
MapRazorComponents<App>().AddInteractiveServerRenderMode() serves
_framework/blazor.web.js from the host assembly (Microsoft.NET.Sdk.Web).
Per MS docs, the root component must be in the server (host) project.

- Move App.razor and Routes.razor from CentralUI to Host/Components/
- Add Host/_Imports.razor for Razor component usings
- Make MapCentralUI generic: MapCentralUI<TApp>() accepts root component
- Add AdditionalAssemblies to discover CentralUI's pages/layouts
- Routes.razor references both Host and CentralUI assemblies
- Fix all DI registrations (TemplateEngine services)
- SCADALINK_CONFIG env var for role-specific config loading

Verified: blazor.web.js HTTP 200 (200KB), login page renders with Blazor
interactive server mode, SignalR circuit establishes, LDAP auth works.

src/ScadaLink.TemplateEngine/ServiceCollectionExtensions.cs

@@ -1,4 +1,7 @@
 using Microsoft.Extensions.DependencyInjection;
+using ScadaLink.TemplateEngine.Flattening;
+using ScadaLink.TemplateEngine.Services;
+using ScadaLink.TemplateEngine.Validation;
 
 namespace ScadaLink.TemplateEngine;
 
@@ -9,6 +12,25 @@ public static class ServiceCollectionExtensions
         services.AddScoped<TemplateService>();
         services.AddScoped<SharedScriptService>();
 
+        // Flattening services (stateless utilities)
+        services.AddTransient<FlatteningService>();
+        services.AddTransient<DiffService>();
+        services.AddTransient<RevisionHashService>();
+
+        // Validation services (stateless utilities)
+        services.AddTransient<ScriptCompiler>();
+        services.AddTransient<SemanticValidator>();
+        services.AddTransient<ValidationService>();
+
+        // Domain services (depend on scoped DbContext / repositories)
+        services.AddScoped<InstanceService>();
+        services.AddScoped<SiteService>();
+        services.AddScoped<AreaService>();
+        services.AddScoped<TemplateDeletionService>();
+
+        // Note: CycleDetector, CollisionDetector, LockEnforcer, and TemplateResolver
+        // are static utility classes and do not require DI registration.
+
         return services;
     }