feat(host): StartupValidator warns when a clustered central keeps per-node inbound API keys; rejects an unknown ApiKeyStore:Provider at boot; Program.cs logs CollectWarnings once Serilog is up

Claude-Session: https://claude.ai/code/session_013L3XdmVii9i5sY4FChU8pB

src/ZB.MOM.WW.ScadaBridge.Host/Program.cs

@@ -162,6 +162,12 @@ try
 {
     Log.Information("Starting ScadaBridge host as {Role} on {Hostname}", nodeRole, nodeHostname);
 
+    // Non-fatal preflight findings (StartupValidator.CollectWarnings) are logged here rather than
+    // inside Validate because the validator runs before Serilog exists. Today: a clustered Central
+    // still on the per-node SQLite inbound API key store (design 2026-09-02, register row 108).
+    foreach (var warning in StartupValidator.CollectWarnings(configuration))
+        Log.Warning("Startup configuration warning: {Warning}", warning);
+
     if (nodeRole.Equals("Central", StringComparison.OrdinalIgnoreCase))
     {
         var builder = WebApplication.CreateBuilder(args);