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/repositories/knowledge_to_agent.py

@@ -0,0 +1,94 @@
+"""
+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.
+"""
+
+from sqlalchemy.orm import Session
+from app.models.knowledge_to_agent import KnowledgeToAgent
+from typing import List, Optional
+from uuid import UUID
+
+class KnowledgeToAgentRepository:
+    def __init__(self, db: Session):
+        self.db = db
+
+    def get_by_ids(self, knowledge_id: int, agent_id: UUID) -> Optional[KnowledgeToAgent]:
+        """Get a link by knowledge_id and agent_id"""
+        return self.db.query(KnowledgeToAgent).filter(
+            KnowledgeToAgent.knowledge_id == knowledge_id,
+            KnowledgeToAgent.agent_id == agent_id
+        ).first()
+
+    def get_by_agent(self, agent_id: UUID) -> List[KnowledgeToAgent]:
+        """Get all knowledge sources for an agent"""
+        return self.db.query(KnowledgeToAgent).filter(
+            KnowledgeToAgent.agent_id == agent_id
+        ).all()
+
+    def get_by_org(self, org_id: UUID) -> List[KnowledgeToAgent]:
+        """Get all knowledge sources for an organization"""
+        return self.db.query(KnowledgeToAgent).filter(
+            KnowledgeToAgent.organization_id == org_id
+        ).all()
+
+    def create(self, knowledge_source: KnowledgeToAgent, commit: bool = True) -> KnowledgeToAgent:
+        """Create a new knowledge source.
+
+        Pass commit=False when the caller has more work that must land in the
+        same transaction — the vector-store filter update in particular, which
+        is what actually makes the link visible to retrieval.
+        """
+        # Check if link already exists
+        existing = self.get_by_ids(
+            knowledge_source.knowledge_id,
+            knowledge_source.agent_id
+        )
+
+        if existing:
+            return existing
+
+        self.db.add(knowledge_source)
+        if commit:
+            self.db.commit()
+            self.db.refresh(knowledge_source)
+        else:
+            self.db.flush()
+        return knowledge_source
+
+    def delete(self, source_id: int) -> bool:
+        """Delete a knowledge source"""
+        source = self.db.query(KnowledgeToAgent).filter(
+            KnowledgeToAgent.id == source_id
+        ).first()
+        if source:
+            self.db.delete(source)
+            self.db.commit()
+            return True
+        return False
+
+    def delete_by_ids(self, knowledge_id: int, agent_id: UUID, commit: bool = True) -> bool:
+        """Delete a link by knowledge and agent IDs.
+
+        See create() for why a caller may want commit=False.
+        """
+        result = self.db.query(KnowledgeToAgent)\
+            .filter(
+                KnowledgeToAgent.knowledge_id == knowledge_id,
+                KnowledgeToAgent.agent_id == agent_id
+        ).delete()
+        if commit:
+            self.db.commit()
+        else:
+            self.db.flush()
+        return bool(result)