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/20260424212250_AddTaskCreatedBy.cs

@@ -0,0 +1,28 @@
+using Microsoft.EntityFrameworkCore.Migrations;
+
+#nullable disable
+
+namespace ClaudeDo.Data.Migrations
+{
+    /// <inheritdoc />
+    public partial class AddTaskCreatedBy : Migration
+    {
+        /// <inheritdoc />
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.AddColumn<string>(
+                name: "created_by",
+                table: "tasks",
+                type: "TEXT",
+                nullable: true);
+        }
+
+        /// <inheritdoc />
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropColumn(
+                name: "created_by",
+                table: "tasks");
+        }
+    }
+}

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");