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/SiteRuntimeOptions.cs

@@ -0,0 +1,20 @@
+namespace ScadaLink.SiteRuntime;
+
+/// <summary>
+/// Configuration options for the Site Runtime component.
+/// Bound from ScadaLink:SiteRuntime configuration section.
+/// </summary>
+public class SiteRuntimeOptions
+{
+    /// <summary>
+    /// Number of Instance Actors to create per batch during staggered startup.
+    /// Default: 20.
+    /// </summary>
+    public int StartupBatchSize { get; set; } = 20;
+
+    /// <summary>
+    /// Delay in milliseconds between startup batches to prevent reconnection storms.
+    /// Default: 100ms.
+    /// </summary>
+    public int StartupBatchDelayMs { get; set; } = 100;
+}