Initial import of the CBDDC codebase with docs and tests. Add a .NET-focused gitignore to keep generated artifacts out of source control.

src/ZB.MOM.WW.CBDDC.Persistence/BLite/Entities/DocumentMetadataEntity.cs

@@ -0,0 +1,47 @@
+using System.ComponentModel.DataAnnotations;
+
+namespace ZB.MOM.WW.CBDDC.Persistence.BLite.Entities;
+
+/// <summary>
+/// BLite entity representing document metadata for sync tracking.
+/// Stores HLC timestamp and deleted state for each document without modifying application entities.
+/// </summary>
+public class DocumentMetadataEntity
+{
+    /// <summary>
+    /// Gets or sets the unique identifier for this entity (technical key).
+    /// Auto-generated GUID string.
+    /// </summary>
+    [Key]
+    public string Id { get; set; } = "";
+
+    /// <summary>
+    /// Gets or sets the collection name (business key part 1).
+    /// </summary>
+    public string Collection { get; set; } = "";
+
+    /// <summary>
+    /// Gets or sets the document key within the collection (business key part 2).
+    /// </summary>
+    public string Key { get; set; } = "";
+
+    /// <summary>
+    /// Gets or sets the physical time component of the HLC timestamp.
+    /// </summary>
+    public long HlcPhysicalTime { get; set; }
+
+    /// <summary>
+    /// Gets or sets the logical counter component of the HLC timestamp.
+    /// </summary>
+    public int HlcLogicalCounter { get; set; }
+
+    /// <summary>
+    /// Gets or sets the node ID that last modified this document.
+    /// </summary>
+    public string HlcNodeId { get; set; } = "";
+
+    /// <summary>
+    /// Gets or sets whether this document is marked as deleted (tombstone).
+    /// </summary>
+    public bool IsDeleted { get; set; }
+}