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/registry.py

@@ -0,0 +1,47 @@
+"""
+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 typing import Dict, Optional
+
+from app.crm.base import CrmAdapter
+
+_adapters: Dict[str, CrmAdapter] = {}
+
+
+def register_adapter(adapter: CrmAdapter) -> CrmAdapter:
+    """Register a stateless adapter singleton for its provider."""
+    _adapters[adapter.provider] = adapter
+    return adapter
+
+
+def get_adapter(provider: str) -> Optional[CrmAdapter]:
+    """Adapter for a CRM provider, or None for unknown providers."""
+    _ensure_loaded()
+    return _adapters.get(provider)
+
+
+_loaded = False
+
+
+def _ensure_loaded() -> None:
+    """Import adapter modules on first use (each registers itself).
+    Lazy so importing app.crm never pulls every adapter's deps."""
+    global _loaded
+    if _loaded:
+        return
+    _loaded = True
+    from app.crm import hubspot  # noqa: F401
+    from app.crm import pipedrive  # noqa: F401