fix: stop user-level gateway service conflicting with system-level one

Root cause: user-level hermes-gateway.service was running the same
-p default gateway as the system-level hermes-gateway@default.service,
causing the two to SIGTERM each other every ~5 minutes. This killed
in-flight Hermes API requests with 'Remote end closed connection'.

Fix: disabled the redundant user-level service.
Also: simplified webhook to just forward raw message content (no
system prompt, no ACK, no max_tokens overrides). Removed unused
_get_ack method.

gateway/linux/wechat_webhook.py

@@ -125,11 +125,10 @@ class WebhookHandler(BaseHTTPRequestHandler):
         self._respond(200, {"status": "ok"})
     
     def _forward_to_hermes(self, sender, sender_id, text):
-        """Forward to Hermes and send reply back to WeChat."""
+        """Forward message to Hermes, get response, send back to WeChat."""
         payload = json.dumps({
             "model": "nova-4",
             "messages": [
-                {"role": "system", "content": "你是莫荷微信Bot。回复简洁，不要废话。"},
                 {"role": "user", "content": f"[微信消息] 来自 {sender}({sender_id}): {text}"}
             ]
         }).encode()
@@ -141,12 +140,11 @@ class WebhookHandler(BaseHTTPRequestHandler):
                 opener = ureq.build_opener(handler)
                 req = ureq.Request(HERMES_API, data=payload,
                     headers={"Content-Type": "application/json", "Authorization": f"Bearer {HERMES_KEY}"})
-                resp = opener.open(req, timeout=30)
+                resp = opener.open(req, timeout=180)
                 resp_data = json.loads(resp.read())
                 reply = resp_data.get('choices', [{}])[0].get('message', {}).get('content', '')
                 log.info(f"Hermes OK, reply: {reply[:60]}")
                 
-                # Send reply back via WeChat API
                 if reply and sender:
                     self._send_wechat(sender, reply)
             except Exception as e: