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.StoreAndForward/ServiceCollectionExtensions.cs

@@ -7,6 +7,10 @@ namespace ScadaLink.StoreAndForward;
 
 public static class ServiceCollectionExtensions
 {
+    /// <summary>
+    /// Registers Store-and-Forward services including storage, the delivery service, and the replication service.
+    /// </summary>
+    /// <param name="services">The service collection to register into.</param>
     public static IServiceCollection AddStoreAndForward(this IServiceCollection services)
     {
         services.AddSingleton<StoreAndForwardStorage>(sp =>
@@ -58,6 +62,10 @@ public static class ServiceCollectionExtensions
         return services;
     }
 
+    /// <summary>
+    /// Registers Store-and-Forward Akka actor bindings. Actor creation is handled by the Host during actor system startup.
+    /// </summary>
+    /// <param name="services">The service collection to register into.</param>
     public static IServiceCollection AddStoreAndForwardActors(this IServiceCollection services)
     {
         // Akka actor registration handled by Host component during actor system startup