feat(models): 组织、用户、角色、客户、会话与消息模型

按组织边界定义数据关系，补齐仓储层与通用工具，迁移脚本可重复执行。

backend/app/models/workflow_node.py

@@ -0,0 +1,85 @@
+"""
+Copyright 2024-2026 ChatterMate
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+"""
+
+from sqlalchemy import Column, String, Text, ForeignKey, JSON, Float, DateTime, Enum
+from sqlalchemy.orm import relationship
+from sqlalchemy.dialects.postgresql import UUID
+from sqlalchemy.sql import func
+from app.database import Base
+import enum
+import uuid
+
+
+class NodeType(str, enum.Enum):
+    MESSAGE = "message"
+    LLM = "llm"
+    CONDITION = "condition"
+    FORM = "form"
+    ACTION = "action"
+    HUMAN_TRANSFER = "human_transfer"
+    WAIT = "wait"
+    END = "end"
+    LANDING_PAGE = "landing_page"
+    USER_INPUT = "user_input"
+    GUARDRAILS = "guardrails"
+
+
+class ActionType(str, enum.Enum):
+    WEBHOOK = "webhook"
+    DATABASE = "database"
+    EMAIL = "email"
+    NOTIFICATION = "notification"
+    CUSTOM = "custom"
+
+
+class ExitCondition(str, enum.Enum):
+    SINGLE_EXECUTION = "single_execution"
+    CONTINUOUS_EXECUTION = "continuous_execution"
+
+
+class WorkflowNode(Base):
+    __tablename__ = "workflow_nodes"
+
+    id = Column(UUID(as_uuid=True), primary_key=True, default=uuid.uuid4)
+    workflow_id = Column(UUID(as_uuid=True), ForeignKey("workflows.id", ondelete="CASCADE"), nullable=False)
+    node_type = Column(Enum(NodeType), nullable=False)
+    name = Column(String(100), nullable=False)
+    description = Column(Text)
+    position_x = Column(Float, default=0)  # X coordinate on canvas
+    position_y = Column(Float, default=0)  # Y coordinate on canvas
+    config = Column(JSON, default={})  # Node-specific configuration
+    created_at = Column(DateTime(timezone=True), server_default=func.now())
+    updated_at = Column(DateTime(timezone=True), server_default=func.now(), onupdate=func.now())
+    
+
+
+    # Relationships
+    workflow = relationship("Workflow", back_populates="nodes")
+    outgoing_connections = relationship(
+        "WorkflowConnection", 
+        foreign_keys="[WorkflowConnection.source_node_id]", 
+        back_populates="source_node",
+        cascade="all, delete-orphan"
+    )
+    incoming_connections = relationship(
+        "WorkflowConnection", 
+        foreign_keys="[WorkflowConnection.target_node_id]", 
+        back_populates="target_node",
+        cascade="all, delete-orphan"
+    )
+
+    class Config:
+        orm_mode = True