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/TaskNote.cs

@@ -0,0 +1,14 @@
+using TaskTracker.Core.Enums;
+
+namespace TaskTracker.Core.Entities;
+
+public class TaskNote
+{
+    public int Id { get; set; }
+    public int WorkTaskId { get; set; }
+    public string Content { get; set; } = string.Empty;
+    public NoteType Type { get; set; }
+    public DateTime CreatedAt { get; set; }
+
+    public WorkTask WorkTask { get; set; } = null!;
+}