Phase 1 WP-1: EF Core DbContext with Fluent API mappings for all 26 entities

ScadaLinkDbContext with 10 configuration classes (Fluent API only), initial
migration creating 25 tables, environment-aware migration helper (auto-apply
dev, validate-only prod), DesignTimeDbContextFactory, optimistic concurrency
on DeploymentRecord. 20 tests verify schema, CRUD, relationships, cascades.

src/ScadaLink.Host/Program.cs

@@ -43,7 +43,10 @@ if (role.Equals("Central", StringComparison.OrdinalIgnoreCase))
     builder.Services.AddSecurity();
     builder.Services.AddCentralUI();
     builder.Services.AddInboundAPI();
-    builder.Services.AddConfigurationDatabase();
+
+    var configDbConnectionString = configuration["ScadaLink:Database:ConfigurationDb"]
+        ?? throw new InvalidOperationException("ScadaLink:Database:ConfigurationDb connection string is required for Central role.");
+    builder.Services.AddConfigurationDatabase(configDbConnectionString);
 
     // Options binding
     BindSharedOptions(builder.Services, builder.Configuration);
@@ -51,6 +54,18 @@ if (role.Equals("Central", StringComparison.OrdinalIgnoreCase))
     builder.Services.Configure<InboundApiOptions>(builder.Configuration.GetSection("ScadaLink:InboundApi"));
 
     var app = builder.Build();
+
+    // Apply or validate database migrations (skip when running in test harness)
+    if (!string.Equals(configuration["ScadaLink:Database:SkipMigrations"], "true", StringComparison.OrdinalIgnoreCase))
+    {
+        var isDevelopment = app.Environment.IsDevelopment();
+        using (var scope = app.Services.CreateScope())
+        {
+            var dbContext = scope.ServiceProvider.GetRequiredService<ScadaLinkDbContext>();
+            await MigrationHelper.ApplyOrValidateMigrationsAsync(dbContext, isDevelopment);
+        }
+    }
+
     app.MapCentralUI();
     app.MapInboundAPI();
     await app.RunAsync();