feat(gateway): add WeCom (Enterprise WeChat) platform support (#3847)

Adds WeCom as a gateway platform adapter using the AI Bot WebSocket
gateway for real-time bidirectional communication. No public endpoint
or new pip dependencies needed (uses existing aiohttp + httpx).

Features:
- WebSocket persistent connection with auto-reconnect (exponential backoff)
- DM and group messaging with configurable access policies
- Media upload/download with AES decryption for encrypted attachments
- Markdown rendering, quote context preservation
- Proactive + passive reply message modes
- Chunked media upload pipeline (512KB chunks)

Cherry-picked from PR #1898 by EvilRan with:
- Moved to current main (PR was 300 commits behind)
- Skipped base.py regressions (reply_to additions are good but belong
  in a separate PR since they affect all platforms)
- Fixed test assertions to match current base class send() signature
  (reply_to=None kwarg now explicit)
- All 16 integration points added surgically to current main
- No new pip dependencies (aiohttp + httpx already installed)

Fixes #1898

Co-authored-by: EvilRan <EvilRan@users.noreply.github.com>

website/docs/user-guide/messaging/index.md

@@ -6,7 +6,7 @@ description: "Chat with Hermes from Telegram, Discord, Slack, WhatsApp, Signal,
 
 # Messaging Gateway
 
-Chat with Hermes from Telegram, Discord, Slack, WhatsApp, Signal, SMS, Email, Home Assistant, Mattermost, Matrix, DingTalk, Feishu/Lark, or your browser. The gateway is a single background process that connects to all your configured platforms, handles sessions, runs cron jobs, and delivers voice messages.
+Chat with Hermes from Telegram, Discord, Slack, WhatsApp, Signal, SMS, Email, Home Assistant, Mattermost, Matrix, DingTalk, Feishu/Lark, WeCom, or your browser. The gateway is a single background process that connects to all your configured platforms, handles sessions, runs cron jobs, and delivers voice messages.
 
 For the full voice feature set — including CLI microphone mode, spoken replies in messaging, and Discord voice-channel conversations — see [Voice Mode](/docs/user-guide/features/voice-mode) and [Use Voice Mode with Hermes](/docs/guides/use-voice-mode-with-hermes).
 
@@ -28,6 +28,7 @@ flowchart TB
             mx[Matrix]
             dt[DingTalk]
     fs[Feishu/Lark]
+    wc[WeCom]
             api["API Server<br/>(OpenAI-compatible)"]
             wh[Webhooks]
         end
@@ -330,6 +331,7 @@ Each platform has its own toolset:
 | Matrix | `hermes-matrix` | Full tools including terminal |
 | DingTalk | `hermes-dingtalk` | Full tools including terminal |
 | Feishu/Lark | `hermes-feishu` | Full tools including terminal |
+| WeCom | `hermes-wecom` | Full tools including terminal |
 | API Server | `hermes` (default) | Full tools including terminal |
 | Webhooks | `hermes-webhook` | Full tools including terminal |
 
@@ -347,5 +349,6 @@ Each platform has its own toolset:
 - [Matrix Setup](matrix.md)
 - [DingTalk Setup](dingtalk.md)
 - [Feishu/Lark Setup](feishu.md)
+- [WeCom Setup](wecom.md)
 - [Open WebUI + API Server](open-webui.md)
 - [Webhooks](webhooks.md)