chore: initial commit of TaskTracker project

Existing ASP.NET API with vanilla JS SPA, WindowWatcher, Chrome extension, and MCP server.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

TaskTracker.Core/Entities/WorkTask.cs

@@ -0,0 +1,22 @@
+using TaskTracker.Core.Enums;
+
+namespace TaskTracker.Core.Entities;
+
+public class WorkTask
+{
+    public int Id { get; set; }
+    public string Title { get; set; } = string.Empty;
+    public string? Description { get; set; }
+    public WorkTaskStatus Status { get; set; }
+    public string? Category { get; set; }
+    public DateTime CreatedAt { get; set; }
+    public DateTime? StartedAt { get; set; }
+    public DateTime? CompletedAt { get; set; }
+
+    public int? ParentTaskId { get; set; }
+    public WorkTask? ParentTask { get; set; }
+    public List<WorkTask> SubTasks { get; set; } = new();
+
+    public List<TaskNote> Notes { get; set; } = [];
+    public List<ContextEvent> ContextEvents { get; set; } = [];
+}