feat(persistence): 4 business ORM models — nullable workspace_id

ORM-side mirror of alembic 0002. threads_meta gets the matching
(workspace_id, user_id, updated_at) composite index so fresh
create_all() dev databases land on the same shape Alembic produces.
Pre-existing test_alembic_default_workspace_id pins to revision
0001 explicitly since 'head' now includes 0002.

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

backend/packages/harness/deerflow/persistence/feedback/model.py

@@ -4,7 +4,7 @@ from __future__ import annotations
 
 from datetime import UTC, datetime
 
-from sqlalchemy import DateTime, String, Text, UniqueConstraint
+from sqlalchemy import DateTime, ForeignKey, String, Text, UniqueConstraint
 from sqlalchemy.orm import Mapped, mapped_column
 
 from deerflow.persistence.base import Base
@@ -22,6 +22,12 @@ class FeedbackRow(Base):
     run_id: Mapped[str] = mapped_column(String(64), nullable=False, index=True, comment="关联的运行 ID（runs.run_id）")
     thread_id: Mapped[str] = mapped_column(String(64), nullable=False, index=True, comment="关联的会话 ID（threads_meta.thread_id）")
     user_id: Mapped[str | None] = mapped_column(String(64), index=True, comment="反馈作者；为 NULL 表示历史无主数据")
+    workspace_id: Mapped[str | None] = mapped_column(
+        String(36),
+        ForeignKey("workspaces.id", ondelete="CASCADE"),
+        nullable=True,
+        comment="所属 workspace；PR5 期间 nullable（回填中），PR5 0003 迁移后改 NOT NULL",
+    )
     message_id: Mapped[str | None] = mapped_column(String(64), comment="可选的 RunEventStore 事件 ID；为 NULL 表示针对整次运行而非单条消息")
     rating: Mapped[int] = mapped_column(nullable=False, comment="评分：+1 点赞，-1 点踩")
     comment: Mapped[str | None] = mapped_column(Text, comment="可选的文字评论")