Initial commit: JDE Scoping Tool migration project

Set up repository with legacy .NET Framework 4.8 source (OLD/),
new .NET 10 Blazor solution (NEW/), OpenSpec specifications,
documentation, and project configuration.

NEW/src/JdeScoping.DataAccess/Exceptions/DataAccessTimeoutException.cs

@@ -0,0 +1,31 @@
+namespace JdeScoping.DataAccess.Exceptions;
+
+/// <summary>
+/// Exception thrown when a database operation times out.
+/// </summary>
+public class DataAccessTimeoutException : DataAccessException
+{
+    /// <summary>
+    /// The configured timeout value in seconds.
+    /// </summary>
+    public int TimeoutSeconds { get; }
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="DataAccessTimeoutException"/> class.
+    /// </summary>
+    /// <param name="message">The error message.</param>
+    /// <param name="timeoutSeconds">The configured timeout value in seconds.</param>
+    /// <param name="operation">The operation that was being performed.</param>
+    /// <param name="repository">The repository where the error occurred.</param>
+    /// <param name="inner">The inner exception.</param>
+    public DataAccessTimeoutException(
+        string message,
+        int timeoutSeconds,
+        string? operation = null,
+        string? repository = null,
+        Exception? inner = null)
+        : base(message, operation, repository, inner)
+    {
+        TimeoutSeconds = timeoutSeconds;
+    }
+}