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/Migrations/ClaudeDoDbContextModelSnapshot.cs

@@ -82,7 +82,7 @@ namespace ClaudeDo.Data.Migrations
                         {
                             Id = 1,
                             DefaultClaudeInstructions = "",
-                            DefaultMaxTurns = 30,
+                            DefaultMaxTurns = 100,
                             DefaultModel = "sonnet",
                             DefaultPermissionMode = "bypassPermissions",
                             WorktreeAutoCleanupDays = 7,
@@ -236,6 +236,10 @@ namespace ClaudeDo.Data.Migrations
                         .HasColumnType("TEXT")
                         .HasColumnName("created_at");
 
+                    b.Property<string>("CreatedBy")
+                        .HasColumnType("TEXT")
+                        .HasColumnName("created_by");
+
                     b.Property<string>("Description")
                         .HasColumnType("TEXT")
                         .HasColumnName("description");