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/utils/business_hours.py

@@ -0,0 +1,83 @@
+"""
+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 datetime import datetime
+
+import pytz
+
+from app.core.logger import get_logger
+
+logger = get_logger(__name__)
+
+# Used when an organization has never configured its hours. Weekdays 9-5 in the
+# org's timezone, weekend closed.
+DEFAULT_BUSINESS_HOURS = {
+    'monday': {'start': '09:00', 'end': '17:00', 'enabled': True},
+    'tuesday': {'start': '09:00', 'end': '17:00', 'enabled': True},
+    'wednesday': {'start': '09:00', 'end': '17:00', 'enabled': True},
+    'thursday': {'start': '09:00', 'end': '17:00', 'enabled': True},
+    'friday': {'start': '09:00', 'end': '17:00', 'enabled': True},
+    'saturday': {'start': '09:00', 'end': '17:00', 'enabled': False},
+    'sunday': {'start': '09:00', 'end': '17:00', 'enabled': False},
+}
+
+_DEFAULT_START = '09:00'
+_DEFAULT_END = '17:00'
+
+
+def organization_timezone(organization) -> pytz.BaseTzInfo:
+    """The org's timezone, falling back to UTC for a missing or bad value."""
+    tz_name = getattr(organization, 'timezone', None) or 'UTC'
+    try:
+        return pytz.timezone(tz_name)
+    except pytz.UnknownTimeZoneError:
+        logger.warning(f"Invalid timezone {tz_name}, using UTC")
+        return pytz.UTC
+
+
+def is_within_business_hours(organization) -> bool:
+    """Whether the organization is open right now, in its own timezone.
+
+    Pure and cheap — no database work and no model call — so it can answer the
+    widget's "are you around?" on every page load, not just when the AI is
+    deciding whether to hand a chat over.
+
+    Note: hours are compared as minutes-of-day, so a window that wraps midnight
+    (22:00-02:00) never matches. That is the behaviour this was extracted from;
+    changing it would change when the AI offers a transfer.
+    """
+    business_hours = getattr(organization, 'business_hours', None) or DEFAULT_BUSINESS_HOURS
+
+    now = datetime.now(organization_timezone(organization))
+    today = business_hours.get(now.strftime('%A').lower(), {
+        'start': _DEFAULT_START,
+        'end': _DEFAULT_END,
+        'enabled': False,
+    })
+
+    if not today.get('enabled', False):
+        return False
+
+    try:
+        start_hour, start_minute = map(int, today.get('start', _DEFAULT_START).split(':'))
+        end_hour, end_minute = map(int, today.get('end', _DEFAULT_END).split(':'))
+    except (ValueError, AttributeError) as e:
+        logger.error(f"Error parsing business hours: {str(e)}")
+        start_hour, start_minute = 9, 0
+        end_hour, end_minute = 17, 0
+
+    minutes_now = now.hour * 60 + now.minute
+    return (start_hour * 60 + start_minute) <= minutes_now <= (end_hour * 60 + end_minute)