feat(data): add Waiting task status and CreatedBy column

- New TaskStatus.Waiting for sequential subtask chains.
- New TaskEntity.CreatedBy column with migration AddTaskCreatedBy.
- TaskRepository.GetByCreatorAsync for filtering by creator.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/ClaudeDo.Data/Configuration/TaskEntityConfiguration.cs

@@ -17,6 +17,7 @@ public class TaskEntityConfiguration : IEntityTypeConfiguration<TaskEntity>
          : v == TaskStatus.Planning ? "planning"
          : v == TaskStatus.Planned ? "planned"
          : v == TaskStatus.Draft ? "draft"
+         : v == TaskStatus.Waiting ? "waiting"
          : throw new ArgumentOutOfRangeException(nameof(v));
 
     private static TaskStatus StatusFromString(string v)
@@ -28,6 +29,7 @@ public class TaskEntityConfiguration : IEntityTypeConfiguration<TaskEntity>
          : v == "planning" ? TaskStatus.Planning
          : v == "planned" ? TaskStatus.Planned
          : v == "draft" ? TaskStatus.Draft
+         : v == "waiting" ? TaskStatus.Waiting
          : throw new ArgumentOutOfRangeException(nameof(v));
 
     private static readonly ValueConverter<TaskStatus, string> StatusConverter =
@@ -64,6 +66,8 @@ public class TaskEntityConfiguration : IEntityTypeConfiguration<TaskEntity>
         builder.Property(t => t.PlanningSessionToken).HasColumnName("planning_session_token");
         builder.Property(t => t.PlanningFinalizedAt).HasColumnName("planning_finalized_at");
 
+        builder.Property(t => t.CreatedBy).HasColumnName("created_by");
+
         builder.HasOne(t => t.Parent)
             .WithMany(t => t.Children)
             .HasForeignKey(t => t.ParentTaskId)