feat(daily-prep): add DailyPrepMaxTasks app setting

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

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

@@ -71,4 +71,21 @@ public class AppSettingsRepositoryTests : IDisposable
 
         Assert.Null(row.CentralWorktreeRoot);
     }
+
+    [Fact]
+    public async Task DailyPrepMaxTasks_defaults_to_5_and_persists()
+    {
+        using var ctx = _db.CreateContext();
+        var repo = new AppSettingsRepository(ctx);
+
+        var initial = await repo.GetAsync();
+        Assert.Equal(5, initial.DailyPrepMaxTasks);
+
+        initial.DailyPrepMaxTasks = 8;
+        await repo.UpdateAsync(initial);
+
+        using var readCtx = _db.CreateContext();
+        var reloaded = await new AppSettingsRepository(readCtx).GetAsync();
+        Assert.Equal(8, reloaded.DailyPrepMaxTasks);
+    }
 }