feat: wire site-local repos, remove config DB from Site, update artifact service

- SiteExternalSystemRepository and SiteNotificationRepository registered in Site DI
- Removed AddConfigurationDatabase from Site role in Program.cs
- Removed ConfigurationDb from appsettings.Site.json
- ArtifactDeploymentService collects all 6 artifact types including data connections and SMTP

src/ScadaLink.Host/Program.cs

@@ -152,14 +152,8 @@ try
             services.AddExternalSystemGateway();
             services.AddNotificationService();
 
-            // Configuration database (read-only access for external system definitions, notification lists)
-            var configDbConnectionString = context.Configuration["ScadaLink:Database:ConfigurationDb"];
-            if (!string.IsNullOrWhiteSpace(configDbConnectionString))
-            {
-                services.AddConfigurationDatabase(configDbConnectionString);
-            }
-
             // Site-only components — AddSiteRuntime registers SiteStorageService with SQLite path
+            // and site-local repository implementations (IExternalSystemRepository, INotificationRepository)
             var siteDbPath = context.Configuration["ScadaLink:Database:SiteDbPath"] ?? "site.db";
             services.AddSiteRuntime($"Data Source={siteDbPath}");
             services.AddDataConnectionLayer();