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/rating.py

@@ -0,0 +1,42 @@
+"""
+Copyright 2024-2026 ReplyPier
+
+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.
+"""
+
+import uuid
+from sqlalchemy import Column, Integer, String, Text, ForeignKey, DateTime
+from sqlalchemy.orm import relationship
+from sqlalchemy.dialects.postgresql import UUID
+from app.database import Base
+from sqlalchemy.sql import func
+
+
+class Rating(Base):
+    __tablename__ = "ratings"
+
+    id = Column(UUID(as_uuid=True), primary_key=True, index=True,default=uuid.uuid4)
+    session_id = Column(UUID(as_uuid=True), ForeignKey("session_to_agents.session_id", ondelete="CASCADE"), nullable=False)
+    customer_id = Column(UUID(as_uuid=True), ForeignKey("customers.id", ondelete="SET NULL"), nullable=True)
+    agent_id = Column(UUID(as_uuid=True), ForeignKey("agents.id", ondelete="SET NULL"), nullable=True)
+    user_id = Column(UUID(as_uuid=True), ForeignKey("users.id", ondelete="SET NULL"), nullable=True)
+    organization_id = Column(UUID(as_uuid=True), ForeignKey("organizations.id", ondelete="CASCADE"), nullable=False)
+    rating = Column(Integer, nullable=False)  # 1-5 star rating
+    feedback = Column(Text, nullable=True)  # Optional feedback text
+    created_at = Column(DateTime(timezone=True), server_default=func.now())
+
+    # Relationships
+    session_assignments = relationship("SessionToAgent", back_populates="ratings")
+    customer = relationship("Customer", back_populates="ratings")
+    agent = relationship("Agent", back_populates="ratings") 
+    user = relationship("User", back_populates="ratings")