feat(customer): 网站客户身份签发与长期负责人绑定

可信客户身份由站点后端签发，长期负责人与本次接待人分开保存。

backend/app/crm/__init__.py

@@ -0,0 +1,27 @@
+"""
+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 app.crm.base import CrmAdapter, OAuthTokens, LeadPayload, CrmPushResult
+from app.crm.registry import get_adapter, register_adapter
+
+__all__ = [
+    "CrmAdapter",
+    "OAuthTokens",
+    "LeadPayload",
+    "CrmPushResult",
+    "get_adapter",
+    "register_adapter",
+]