Phase 3A: Site runtime foundation — Akka cluster, SQLite persistence, Deployment Manager singleton, Instance Actor

- WP-1: Site cluster config (keep-oldest SBR, down-if-alone, 2s/10s failure detection)
- WP-2: Site-role host bootstrap (no Kestrel, SQLite paths)
- WP-3: SiteStorageService with deployed_configurations + static_attribute_overrides tables
- WP-4: DeploymentManagerActor as cluster singleton with staggered Instance Actor creation,
  OneForOneStrategy/Resume supervision, deploy/disable/enable/delete lifecycle
- WP-5: InstanceActor with attribute state, GetAttribute/SetAttribute, SQLite override persistence
- WP-6: CoordinatedShutdown verified for graceful singleton handover
- WP-7: Dual-node recovery (both seed nodes, min-nr-of-members=1)
- WP-8: 31 tests (storage CRUD, actor lifecycle, supervision, negative checks)
389 total tests pass, zero warnings.

src/ScadaLink.SiteRuntime/Persistence/SiteStorageInitializer.cs

@@ -0,0 +1,24 @@
+using Microsoft.Extensions.Hosting;
+
+namespace ScadaLink.SiteRuntime.Persistence;
+
+/// <summary>
+/// Hosted service that initializes the SQLite schema on startup.
+/// Runs before the Akka actor system starts creating actors.
+/// </summary>
+public class SiteStorageInitializer : IHostedService
+{
+    private readonly SiteStorageService _storage;
+
+    public SiteStorageInitializer(SiteStorageService storage)
+    {
+        _storage = storage;
+    }
+
+    public async Task StartAsync(CancellationToken cancellationToken)
+    {
+        await _storage.InitializeAsync();
+    }
+
+    public Task StopAsync(CancellationToken cancellationToken) => Task.CompletedTask;
+}