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/fcm_token.py

@@ -0,0 +1,115 @@
+"""
+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.exc import IntegrityError
+from sqlalchemy.orm import Session
+from uuid import UUID
+from typing import List, Sequence
+
+from app.models.fcm_token import FCMToken
+from app.core.logger import get_logger
+
+logger = get_logger(__name__)
+
+
+class FCMTokenRepository:
+    """Web-push tokens, one row per signed-in browser."""
+
+    def __init__(self, db: Session):
+        self.db = db
+
+    def register(self, user_id: UUID, token: str) -> bool:
+        """Store `token` for `user_id`, creating or reassigning its row.
+
+        FCM hands the same token back to a given browser install no matter who
+        is signed in, so an existing row is moved to the current user rather
+        than duplicated — otherwise a shared browser would keep receiving the
+        previous account's notifications.
+        """
+        try:
+            if self._claim(user_id, token):
+                return True
+            # Lost the insert race: the client posts on every app load, so two
+            # tabs opening together both see no row and both insert. Re-run
+            # against the row the winner committed instead of failing the
+            # request and leaving this browser unregistered for the session.
+            self.db.rollback()
+            return self._claim(user_id, token)
+        except Exception as e:
+            logger.error(f"Error registering FCM token: {str(e)}")
+            self.db.rollback()
+            return False
+
+    def _claim(self, user_id: UUID, token: str) -> bool:
+        """Point `token` at `user_id`. False if a concurrent insert won."""
+        existing = self.db.query(FCMToken).filter(
+            FCMToken.token == token).first()
+
+        if existing:
+            if existing.user_id != user_id:
+                logger.info(
+                    f"Reassigning FCM token from user {existing.user_id} to {user_id}")
+                existing.user_id = user_id
+        else:
+            self.db.add(FCMToken(user_id=user_id, token=token))
+
+        try:
+            self.db.commit()
+            return True
+        except IntegrityError:
+            return False
+
+    def get_tokens(self, user_id: UUID) -> List[str]:
+        """Every device token registered for a user."""
+        try:
+            rows = self.db.query(FCMToken.token).filter(
+                FCMToken.user_id == user_id).all()
+            return [row.token for row in rows]
+        except Exception as e:
+            logger.error(f"Error getting FCM tokens: {str(e)}")
+            return []
+
+    def remove(self, user_id: UUID, token: str) -> bool:
+        """Drop a single device's token — used on logout.
+
+        Scoped to the owner so a stolen token can't be used to silence someone
+        else's notifications.
+        """
+        try:
+            deleted = self.db.query(FCMToken).filter(
+                FCMToken.user_id == user_id,
+                FCMToken.token == token,
+            ).delete(synchronize_session=False)
+            self.db.commit()
+            return deleted > 0
+        except Exception as e:
+            logger.error(f"Error removing FCM token: {str(e)}")
+            self.db.rollback()
+            return False
+
+    def remove_tokens(self, tokens: Sequence[str]) -> int:
+        """Drop tokens FCM has told us are dead. Returns the number removed."""
+        if not tokens:
+            return 0
+        try:
+            deleted = self.db.query(FCMToken).filter(
+                FCMToken.token.in_(list(tokens))).delete(synchronize_session=False)
+            self.db.commit()
+            return deleted
+        except Exception as e:
+            logger.error(f"Error pruning FCM tokens: {str(e)}")
+            self.db.rollback()
+            return 0