feat(modules): 帮助中心、工单、工作流与多渠道接入

补齐 FAQ、帮助中心、工单、可视化工作流及 Telegram/WhatsApp/Slack 等渠道模块。

backend/app/services/help_center_access.py

@@ -0,0 +1,42 @@
+"""
+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.
+
+Help-center plan gating: Pro-only on cloud, unrestricted for OSS/self-hosted.
+Thin wrappers over the generic feature gate.
+"""
+
+from uuid import UUID
+
+from sqlalchemy.orm import Session
+
+from app.services.feature_gate import check_feature_access, feature_allowed
+
+HELP_CENTER_FEATURE = "help_center"
+
+UPGRADE_MESSAGE = (
+    "The Help Center is not available in your current plan. "
+    "Please upgrade to Pro to access this feature."
+)
+
+
+def help_center_allowed(db: Session, organization_id: UUID) -> bool:
+    """Non-raising check — used by the public site (which 404s instead of
+    403ing) and the auto-generation hook. Fails closed on gating errors."""
+    return feature_allowed(db, organization_id, HELP_CENTER_FEATURE)
+
+
+def check_help_center_access(db: Session, organization_id: UUID) -> None:
+    """Raising check for admin endpoints (403 with the upgrade message)."""
+    check_feature_access(db, organization_id, HELP_CENTER_FEATURE, UPGRADE_MESSAGE)