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.NotificationService/NotificationDeliveryService.cs

@@ -24,6 +24,15 @@ public class NotificationDeliveryService : INotificationDeliveryService, IDispos
     private readonly ILogger<NotificationDeliveryService> _logger;
     private readonly NotificationOptions _options;
 
+    /// <summary>
+    /// Initializes a new instance of the NotificationDeliveryService with the specified dependencies.
+    /// </summary>
+    /// <param name="repository">The notification repository for data access.</param>
+    /// <param name="smtpClientFactory">Factory for creating SMTP client instances.</param>
+    /// <param name="logger">Logger for diagnostic messages.</param>
+    /// <param name="tokenService">Optional OAuth2 token service for authentication.</param>
+    /// <param name="storeAndForward">Optional store-and-forward service for handling transient failures.</param>
+    /// <param name="options">Optional notification options with fallback values.</param>
     public NotificationDeliveryService(
         INotificationRepository repository,
         Func<ISmtpClientWrapper> smtpClientFactory,
@@ -42,9 +51,7 @@ public class NotificationDeliveryService : INotificationDeliveryService, IDispos
         _options = options?.Value ?? new NotificationOptions();
     }
 
-    /// <summary>
-    /// Sends a notification to a named list. BCC delivery, plain text.
-    /// </summary>
+    /// <inheritdoc />
     public async Task<NotificationResult> SendAsync(
         string listName,
         string subject,
@@ -176,6 +183,8 @@ public class NotificationDeliveryService : INotificationDeliveryService, IDispos
     /// delivery. Returns true on success, false on permanent failure (the message
     /// is parked); throws on a transient failure so the engine retries.
     /// </summary>
+    /// <param name="message">The buffered store-and-forward message to deliver.</param>
+    /// <param name="cancellationToken">Cancellation token for the delivery attempt.</param>
     public async Task<bool> DeliverBufferedAsync(
         StoreAndForwardMessage message, CancellationToken cancellationToken = default)
     {
@@ -347,6 +356,11 @@ public class NotificationDeliveryService : INotificationDeliveryService, IDispos
     /// Delivers an email via SMTP. Throws on failure (transient errors and
     /// <see cref="SmtpPermanentException"/> propagate; the caller classifies them).
     /// </summary>
+    /// <param name="config">The SMTP configuration to use for the connection.</param>
+    /// <param name="recipients">The list of recipients to deliver to.</param>
+    /// <param name="subject">The email subject line.</param>
+    /// <param name="body">The plain-text email body.</param>
+    /// <param name="cancellationToken">Cancellation token for the delivery.</param>
     internal async Task DeliverAsync(
         SmtpConfiguration config,
         IReadOnlyList<NotificationRecipient> recipients,