feat(backend): knowledge iteration + vision + neo4j + response contract source

dependencies.py 拆分为 dependencies/ 包; 新增 vision/ragflow_ingestion/neo4j 客户端与 h5_ai_task; alembic 045 图置信度迁移; 响应契约统一收尾。

backend/app/models/knowledge_base.py

@@ -8,7 +8,7 @@
 
 import uuid
 from datetime import datetime
-from typing import List
+from typing import List, Optional
 
 from sqlalchemy import DateTime, Index, Integer, JSON, String, Text
 from sqlalchemy.orm import Mapped, mapped_column
@@ -93,6 +93,25 @@ class KnowledgeBase(Base):
         comment="使用次数",
     )
 
+    # --------------------------------------------------------------------------
+    # Tier0 扩展字段 — 图同步状态（D1 解读2 合一）
+    # --------------------------------------------------------------------------
+
+    # 图同步状态（pending / synced / failed）
+    graph_sync_status: Mapped[str] = mapped_column(
+        String(20),
+        nullable=False,
+        default="pending",
+        comment="图同步状态：pending / synced / failed",
+    )
+
+    # 关联 Neo4j Issue 节点的 uuid（写入图后回填）
+    graph_node_uuid: Mapped[Optional[str]] = mapped_column(
+        String(36),
+        nullable=True,
+        comment="关联 Neo4j Issue 节点的 uuid",
+    )
+
     # 创建时间
     created_at: Mapped[datetime] = mapped_column(
         DateTime(timezone=True),