feat(data,worker): add db schema init and signalr hub skeleton

Data layer: Paths helper with ~/%USERPROFILE% expansion, SqliteConnectionFactory
(WAL + foreign keys), SchemaInitializer that applies the embedded schema.sql, and
POCO entities for lists/tasks/tags/worktrees.

Worker: WorkerConfig loader (~/.todo-app/worker.config.json with defaults),
WorkerHub exposing Ping(), and Program.cs wiring Kestrel to 127.0.0.1:<port>,
SignalR at /hub, schema applied on startup.

Pins Microsoft.Data.Sqlite and Microsoft.Extensions.Hosting to 8.x for net8.0
compatibility.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/ClaudeDo.Data/Models/TaskEntity.cs

@@ -0,0 +1,26 @@
+namespace ClaudeDo.Data.Models;
+
+public enum TaskStatus
+{
+    Manual,
+    Queued,
+    Running,
+    Done,
+    Failed,
+}
+
+public sealed class TaskEntity
+{
+    public required string Id { get; init; }
+    public required string ListId { get; init; }
+    public required string Title { get; set; }
+    public string? Description { get; set; }
+    public TaskStatus Status { get; set; } = TaskStatus.Manual;
+    public DateTime? ScheduledFor { get; set; }
+    public string? Result { get; set; }
+    public string? LogPath { get; set; }
+    public required DateTime CreatedAt { get; init; }
+    public DateTime? StartedAt { get; set; }
+    public DateTime? FinishedAt { get; set; }
+    public string CommitType { get; set; } = "chore";
+}