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/schemas/lead_capture.py

@@ -0,0 +1,69 @@
+"""
+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 pydantic import BaseModel, ConfigDict, Field, field_validator
+from typing import Optional, List, Dict, Any
+from uuid import UUID
+
+# Reuse the ORM enums so the API contract can never drift from the DB.
+from app.models.lead_capture import LeadAssignmentMode, CrmSyncTarget
+
+# Guardrails to keep the config small.
+MAX_FIELDS = 30
+
+
+class LeadField(BaseModel):
+    """A detail to collect. Standard fields (email/name/company/phone) carry
+    standard=True; custom fields add a label and optional allowed values — which
+    the agent uses to steer/normalise the answer in conversation (no form)."""
+    key: str
+    standard: bool = False
+    enabled: bool = True
+    required: bool = False
+    label: Optional[str] = Field(default=None, max_length=100)
+    options: Optional[List[str]] = None
+
+
+class LeadCaptureConfigBase(BaseModel):
+    enabled: bool = False
+    # GDPR: require the visitor's explicit consent before recording a lead.
+    require_consent: bool = True
+    # Optional free-text steering, appended to the agent's prompt.
+    guidance: Optional[str] = Field(default=None, max_length=2000)
+    fields: List[LeadField] = Field(default_factory=list, max_length=MAX_FIELDS)
+    # Routing config — persisted only; no CRM/Slack/assignment side effects in phase 1.
+    assignment_mode: LeadAssignmentMode = LeadAssignmentMode.NONE
+    assignment_target_user_id: Optional[UUID] = None
+    crm_sync_target: CrmSyncTarget = CrmSyncTarget.NONE
+    slack_notify_enabled: bool = False
+
+
+class LeadCaptureConfigUpdate(LeadCaptureConfigBase):
+    """Full-replace payload for the whole Lead Capture tab (mirrors how the
+    customization tab saves its entire object in one call)."""
+    pass
+
+
+class LeadCaptureConfigResponse(LeadCaptureConfigBase):
+    model_config = ConfigDict(from_attributes=True)
+
+    agent_id: UUID
+
+    @field_validator("fields", mode="before")
+    @classmethod
+    def _coerce_null_json(cls, v):
+        # JSON column defaults to NULL in the DB; present it as an empty list.
+        return v or []