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/SnapshotMetadataEntity.cs

@@ -0,0 +1,36 @@
+using System.ComponentModel.DataAnnotations;
+
+namespace ZB.MOM.WW.CBDDC.Persistence.BLite.Entities;
+
+/// <summary>
+/// BLite entity representing snapshot metadata (oplog pruning checkpoint).
+/// </summary>
+public class SnapshotMetadataEntity
+{
+    /// <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 node identifier (business key).
+    /// </summary>
+    public string NodeId { get; set; } = "";
+
+    /// <summary>
+    /// Gets or sets the physical time component of the timestamp.
+    /// </summary>
+    public long TimestampPhysicalTime { get; set; }
+
+    /// <summary>
+    /// Gets or sets the logical counter component of the timestamp.
+    /// </summary>
+    public int TimestampLogicalCounter { get; set; }
+
+    /// <summary>
+    /// Gets or sets the hash of the snapshot.
+    /// </summary>
+    public string Hash { get; set; } = "";
+}