fix(host): resolve Host-012..015 — consume DownIfAlone in HOCON, sub-second timing precision, config-driven Serilog sinks, transient-only startup retry

src/ScadaLink.Host/Program.cs

@@ -40,11 +40,12 @@ var siteId = configuration["ScadaLink:Node:SiteId"] ?? "central";
 
 // WP-14: Serilog structured logging.
 // Host-011: minimum level is driven by ScadaLink:Logging:MinimumLevel (LoggingOptions).
+// Host-014: console and file sinks are defined in the `Serilog` configuration
+// section (appsettings.json) and applied via ReadFrom.Configuration inside the
+// factory — the sink set, output template, file path and rolling interval are all
+// configuration-driven per REQ-HOST-8, not hard-coded here.
 Log.Logger = ScadaLink.Host.LoggerConfigurationFactory
     .Build(configuration, nodeRole, siteId, nodeHostname)
-    .WriteTo.Console(outputTemplate:
-        "[{Timestamp:HH:mm:ss} {Level:u3}] [{NodeRole}/{NodeHostname}] {Message:lj}{NewLine}{Exception}")
-    .WriteTo.File("logs/scadalink-.log", rollingInterval: Serilog.RollingInterval.Day)
     .CreateLogger();
 
 try
@@ -121,6 +122,8 @@ try
             // Host-010: tolerate a database that is briefly unreachable at boot
             // (e.g. app and DB containers starting together) with a bounded
             // exponential backoff before failing fatally.
+            // Host-015: only connection-class (transient) faults are retried — a
+            // schema-version mismatch is permanent and must fail fast on attempt 1.
             await StartupRetry.ExecuteWithRetryAsync(
                 "database-migration",
                 async () =>
@@ -131,7 +134,8 @@ try
                 },
                 maxAttempts: 8,
                 initialDelay: TimeSpan.FromSeconds(2),
-                migrationLogger);
+                migrationLogger,
+                isTransient: StartupRetry.IsTransientDatabaseFault);
         }
 
         // Middleware pipeline