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/channels/interactive_limits.py

@@ -0,0 +1,60 @@
+"""
+Copyright 2024-2026 ReplyPier
+
+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.
+
+What each channel's tappable choices can hold. Dependency-free so adapters
+(channels/base.py) and the builders (channels/interactive.py) can share it.
+"""
+
+from dataclasses import dataclass
+
+from app.channels.constants import MAX_CHOICE_LENGTH, MAX_CHOICE_OPTIONS
+
+
+@dataclass(frozen=True)
+class InteractiveLimits:
+    max_buttons: int
+    button_title_max: int
+    body_max: int
+    # Choice ids are checked in bytes: Telegram counts bytes, and so does
+    # every other platform's limit once an id isn't ASCII
+    id_max_bytes: int
+    supports_list: bool = False
+    max_list_rows: int = 0
+    row_title_max: int = 0
+    row_description_max: int = 0
+    supports_cta: bool = False
+    # Also write the choices into the text: where some of the platform's
+    # apps don't show the buttons (Instagram on desktop and the web)
+    options_in_text: bool = False
+
+
+# https://developers.facebook.com/docs/whatsapp/cloud-api/messages/interactive-reply-buttons-messages
+WHATSAPP_LIMITS = InteractiveLimits(
+    max_buttons=3, button_title_max=20, body_max=1024, id_max_bytes=256,
+    supports_list=True, max_list_rows=MAX_CHOICE_OPTIONS, row_title_max=24,
+    row_description_max=MAX_CHOICE_LENGTH, supports_cta=True,
+)
+
+# Quick replies: https://developers.facebook.com/docs/messenger-platform/send-messages/quick-replies
+# body_max is each channel's cap on a message's text, which the adapters use too
+MESSENGER_LIMITS = InteractiveLimits(max_buttons=13, button_title_max=20, body_max=2000, id_max_bytes=1000)
+
+# Same quick replies, but Instagram doesn't show them on desktop or the web
+INSTAGRAM_LIMITS = InteractiveLimits(max_buttons=13, button_title_max=20, body_max=1000, id_max_bytes=1000,
+                                     options_in_text=True)
+
+# Inline keyboard: https://core.telegram.org/bots/api#inlinekeyboardbutton
+TELEGRAM_LIMITS = InteractiveLimits(max_buttons=MAX_CHOICE_OPTIONS, button_title_max=64, body_max=4096,
+                                    id_max_bytes=64)