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.Commons/Interfaces/Repositories/INotificationOutboxRepository.cs

@@ -22,6 +22,9 @@ public interface INotificationOutboxRepository
     /// row was inserted, <c>false</c> when an existing row was left untouched.
     /// Commits internally — this call is its own transaction.
     /// </summary>
+    /// <param name="n">The notification to insert.</param>
+    /// <param name="cancellationToken">Cancellation token.</param>
+    /// <returns>True if inserted, false if already exists.</returns>
     Task<bool> InsertIfNotExistsAsync(Notification n, CancellationToken cancellationToken = default);
 
     /// <summary>
@@ -30,21 +33,35 @@ public interface INotificationOutboxRepository
     /// Terminal rows are excluded. Ordered by <c>CreatedAt</c> ascending, capped at
     /// <paramref name="batchSize"/>.
     /// </summary>
+    /// <param name="now">The current time for evaluating due retries.</param>
+    /// <param name="batchSize">Maximum number of rows to return.</param>
+    /// <param name="cancellationToken">Cancellation token.</param>
+    /// <returns>A list of notifications ready for delivery.</returns>
     Task<IReadOnlyList<Notification>> GetDueAsync(DateTimeOffset now, int batchSize, CancellationToken cancellationToken = default);
 
     /// <summary>Returns the notification with the given id, or <c>null</c>.</summary>
+    /// <param name="notificationId">The notification identifier.</param>
+    /// <param name="cancellationToken">Cancellation token.</param>
+    /// <returns>The notification, or null if not found.</returns>
     Task<Notification?> GetByIdAsync(string notificationId, CancellationToken cancellationToken = default);
 
     /// <summary>
     /// Marks <paramref name="n"/> modified and persists it (status transitions).
     /// Commits internally — this call is its own transaction.
     /// </summary>
+    /// <param name="n">The notification to update.</param>
+    /// <param name="cancellationToken">Cancellation token.</param>
     Task UpdateAsync(Notification n, CancellationToken cancellationToken = default);
 
     /// <summary>
     /// Returns a page of notifications matching <paramref name="filter"/>, ordered by
     /// <c>CreatedAt</c> descending, together with the total matching count.
     /// </summary>
+    /// <param name="filter">The query filter.</param>
+    /// <param name="pageNumber">The page number (1-based).</param>
+    /// <param name="pageSize">The page size.</param>
+    /// <param name="cancellationToken">Cancellation token.</param>
+    /// <returns>A tuple of rows and total count.</returns>
     Task<(IReadOnlyList<Notification> Rows, int TotalCount)> QueryAsync(
         NotificationOutboxFilter filter, int pageNumber, int pageSize, CancellationToken cancellationToken = default);
 
@@ -52,6 +69,9 @@ public interface INotificationOutboxRepository
     /// Bulk-deletes terminal rows (Delivered/Parked/Discarded) whose <c>CreatedAt</c> is
     /// older than <paramref name="cutoff"/>. Returns the number of rows deleted.
     /// </summary>
+    /// <param name="cutoff">The cutoff time for deletion.</param>
+    /// <param name="cancellationToken">Cancellation token.</param>
+    /// <returns>The number of rows deleted.</returns>
     Task<int> DeleteTerminalOlderThanAsync(DateTimeOffset cutoff, CancellationToken cancellationToken = default);
 
     /// <summary>
@@ -59,6 +79,10 @@ public interface INotificationOutboxRepository
     /// delivered cutoffs are supplied by the caller; the current time used for
     /// <c>OldestPendingAge</c> is captured inside the method.
     /// </summary>
+    /// <param name="stuckCutoff">The time threshold for marking notifications as stuck.</param>
+    /// <param name="deliveredSince">The time threshold for counting delivered notifications.</param>
+    /// <param name="cancellationToken">Cancellation token.</param>
+    /// <returns>A KPI snapshot.</returns>
     Task<NotificationKpiSnapshot> ComputeKpisAsync(
         DateTimeOffset stuckCutoff, DateTimeOffset deliveredSince, CancellationToken cancellationToken = default);
 
@@ -68,6 +92,10 @@ public interface INotificationOutboxRepository
     /// are supplied by the caller; the current time used for <c>OldestPendingAge</c> is
     /// captured inside the method.
     /// </summary>
+    /// <param name="stuckCutoff">The time threshold for marking notifications as stuck.</param>
+    /// <param name="deliveredSince">The time threshold for counting delivered notifications.</param>
+    /// <param name="cancellationToken">Cancellation token.</param>
+    /// <returns>A list of per-site KPI snapshots.</returns>
     Task<IReadOnlyList<SiteNotificationKpiSnapshot>> ComputePerSiteKpisAsync(
         DateTimeOffset stuckCutoff, DateTimeOffset deliveredSince, CancellationToken cancellationToken = default);
 
@@ -76,5 +104,7 @@ public interface INotificationOutboxRepository
     /// multiple changes for a single commit; the individual mutating methods on this
     /// interface already commit on their own.
     /// </summary>
+    /// <param name="cancellationToken">Cancellation token.</param>
+    /// <returns>The number of changes persisted.</returns>
     Task<int> SaveChangesAsync(CancellationToken cancellationToken = default);
 }