feat: 租户管理体系建设 CRUD + 各业务模块接入 tenant_id

1. 新增 Tenant 模型（tenants 表），支持租户创建、重命名、删除
2. 新增 /api/tenants CRUD 蓝图，default 租户不可删除
3. 数据库初始化时自动创建默认租户记录
4. Dashboard 新增租户管理标签页（创建/编辑/删除租户）
5. 各业务模块写入数据时正确传递 tenant_id：
   - realtime_chat: create_session 和 _save_conversation 支持 tenant_id
   - dialogue_manager: _save_conversation 和 create_work_order 支持 tenant_id
   - conversation_history: save_conversation 支持 tenant_id
   - workorder_sync: sync_from_feishu 支持 tenant_id
   - websocket_server: create_session 传递 tenant_id
   - HTTP chat API: create_session 传递 tenant_id
   - feishu_sync API: 同步时传递 tenant_id
   - workorders API: 创建工单时传递 tenant_id
6. 网页对话入口添加租户选择器
7. 知识库搜索按租户隔离（realtime_chat 中 _search_knowledge 传递 tenant_id）
8. 初始化时自动加载租户列表填充选择器

src/web/blueprints/tenants.py

@@ -0,0 +1,132 @@
+# -*- coding: utf-8 -*-
+"""
+租户管理蓝图
+处理租户 CRUD 的 API 路由
+"""
+
+import json
+import logging
+from flask import Blueprint, request, jsonify
+from src.core.database import db_manager
+from src.core.models import Tenant, DEFAULT_TENANT
+
+logger = logging.getLogger(__name__)
+
+tenants_bp = Blueprint('tenants', __name__, url_prefix='/api/tenants')
+
+
+def _ensure_default_tenant():
+    """确保 default 租户存在"""
+    try:
+        with db_manager.get_session() as session:
+            existing = session.query(Tenant).filter(Tenant.tenant_id == DEFAULT_TENANT).first()
+            if not existing:
+                session.add(Tenant(
+                    tenant_id=DEFAULT_TENANT,
+                    name="默认租户",
+                    description="系统默认租户"
+                ))
+                session.commit()
+    except Exception as e:
+        logger.error(f"确保默认租户失败: {e}")
+
+
+@tenants_bp.route('', methods=['GET'])
+def list_tenants():
+    """获取所有租户列表"""
+    try:
+        with db_manager.get_session() as session:
+            tenants = session.query(Tenant).order_by(Tenant.created_at).all()
+            return jsonify([t.to_dict() for t in tenants])
+    except Exception as e:
+        logger.error(f"获取租户列表失败: {e}")
+        return jsonify({"error": str(e)}), 500
+
+
+@tenants_bp.route('', methods=['POST'])
+def create_tenant():
+    """创建新租户"""
+    try:
+        data = request.get_json()
+        if not data or not data.get('tenant_id') or not data.get('name'):
+            return jsonify({"error": "tenant_id 和 name 为必填项"}), 400
+
+        tenant_id = data['tenant_id'].strip()
+        name = data['name'].strip()
+
+        if not tenant_id or not name:
+            return jsonify({"error": "tenant_id 和 name 不能为空"}), 400
+
+        with db_manager.get_session() as session:
+            existing = session.query(Tenant).filter(Tenant.tenant_id == tenant_id).first()
+            if existing:
+                return jsonify({"error": f"租户 '{tenant_id}' 已存在"}), 409
+
+            tenant = Tenant(
+                tenant_id=tenant_id,
+                name=name,
+                description=data.get('description', ''),
+                config=json.dumps(data.get('config', {}))
+            )
+            session.add(tenant)
+            session.commit()
+
+            # 重新查询以获取完整数据
+            tenant = session.query(Tenant).filter(Tenant.tenant_id == tenant_id).first()
+            return jsonify({"success": True, "tenant": tenant.to_dict()}), 201
+
+    except Exception as e:
+        logger.error(f"创建租户失败: {e}")
+        return jsonify({"error": str(e)}), 500
+
+
+@tenants_bp.route('/<tenant_id>', methods=['PUT'])
+def update_tenant(tenant_id):
+    """更新租户信息（重命名等）"""
+    try:
+        data = request.get_json()
+        if not data:
+            return jsonify({"error": "请求体不能为空"}), 400
+
+        with db_manager.get_session() as session:
+            tenant = session.query(Tenant).filter(Tenant.tenant_id == tenant_id).first()
+            if not tenant:
+                return jsonify({"error": f"租户 '{tenant_id}' 不存在"}), 404
+
+            if 'name' in data:
+                tenant.name = data['name'].strip()
+            if 'description' in data:
+                tenant.description = data['description']
+            if 'config' in data:
+                tenant.config = json.dumps(data['config'])
+            if 'is_active' in data:
+                tenant.is_active = data['is_active']
+
+            session.commit()
+            tenant = session.query(Tenant).filter(Tenant.tenant_id == tenant_id).first()
+            return jsonify({"success": True, "tenant": tenant.to_dict()})
+
+    except Exception as e:
+        logger.error(f"更新租户失败: {e}")
+        return jsonify({"error": str(e)}), 500
+
+
+@tenants_bp.route('/<tenant_id>', methods=['DELETE'])
+def delete_tenant(tenant_id):
+    """删除租户（不允许删除 default）"""
+    try:
+        if tenant_id == DEFAULT_TENANT:
+            return jsonify({"error": "不能删除默认租户"}), 403
+
+        with db_manager.get_session() as session:
+            tenant = session.query(Tenant).filter(Tenant.tenant_id == tenant_id).first()
+            if not tenant:
+                return jsonify({"error": f"租户 '{tenant_id}' 不存在"}), 404
+
+            session.delete(tenant)
+            session.commit()
+            return jsonify({"success": True, "message": f"租户 '{tenant_id}' 已删除"})
+
+    except Exception as e:
+        logger.error(f"删除租户失败: {e}")
+        return jsonify({"error": str(e)}), 500