docs: add XML doc comments across src + Sister Projects section in CLAUDE.md

Bulk CommentChecker pass: fills in <param>/<inheritdoc> tags on public
APIs across all 23 src/ projects so the doc-coverage gate is green. Also
adds a Sister Projects section to CLAUDE.md pointing at the MxAccess
Gateway and OtOpcUa sibling repos, and gitignores local credential
captures (*login*.txt) and the wonder-app-vd03 deploy/ artifacts.

src/ScadaLink.Host/SiteServiceRegistration.cs

@@ -20,6 +20,9 @@ namespace ScadaLink.Host;
 /// </summary>
 public static class SiteServiceRegistration
 {
+    /// <summary>Registers all DI services required for the site role.</summary>
+    /// <param name="services">The service collection to register into.</param>
+    /// <param name="config">Application configuration for options binding.</param>
     public static void Configure(IServiceCollection services, IConfiguration config)
     {
         // Shared components
@@ -88,6 +91,9 @@ public static class SiteServiceRegistration
         services.Configure<SiteEventLogOptions>(config.GetSection("ScadaLink:SiteEventLog"));
     }
 
+    /// <summary>Binds shared options sections (Node, Cluster, Database, Communication, etc.) used by both site and central roles.</summary>
+    /// <param name="services">The service collection to bind options into.</param>
+    /// <param name="config">Application configuration supplying the option values.</param>
     public static void BindSharedOptions(IServiceCollection services, IConfiguration config)
     {
         services.Configure<NodeOptions>(config.GetSection("ScadaLink:Node"));