feat(worker,ui): wire EF Core into DI and update all consumers to IDbContextFactory

Worker and App Program.cs: replace SqliteConnectionFactory+SchemaInitializer
with AddDbContextFactory<ClaudeDoDbContext> + Database.Migrate(). Repos
changed from AddSingleton to AddScoped.

All singleton services (QueueService, StaleTaskRecovery, WorktreeManager,
TaskRunner) and singleton ViewModels (MainWindowViewModel, TaskDetailViewModel,
TaskListViewModel, TaskEditorViewModel) now take IDbContextFactory<ClaudeDoDbContext>
and create short-lived contexts per operation.

Test infrastructure: DbFixture now uses EF migrations instead of SchemaInitializer;
all test classes create contexts via DbFixture.CreateContext().

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

tests/ClaudeDo.Worker.Tests/Repositories/ListRepositoryTests.cs

@@ -1,3 +1,4 @@
+using ClaudeDo.Data;
 using ClaudeDo.Data.Models;
 using ClaudeDo.Data.Repositories;
 using ClaudeDo.Worker.Tests.Infrastructure;
@@ -7,16 +8,22 @@ namespace ClaudeDo.Worker.Tests.Repositories;
 public sealed class ListRepositoryTests : IDisposable
 {
     private readonly DbFixture _db = new();
+    private readonly ClaudeDoDbContext _ctx;
     private readonly ListRepository _lists;
     private readonly TagRepository _tags;
 
     public ListRepositoryTests()
     {
-        _lists = new ListRepository(_db.Factory);
-        _tags = new TagRepository(_db.Factory);
+        _ctx = _db.CreateContext();
+        _lists = new ListRepository(_ctx);
+        _tags = new TagRepository(_ctx);
     }
 
-    public void Dispose() => _db.Dispose();
+    public void Dispose()
+    {
+        _ctx.Dispose();
+        _db.Dispose();
+    }
 
     [Fact]
     public async Task AddAsync_And_GetByIdAsync_Roundtrips()