v2.3.3: fix Discord webhook always failing (Cloudflare blocks Python UA)

Cloudflare protects Discord webhook endpoints and rejects requests
with the default Python urllib User-Agent ('Python-urllib/3.x') with
HTTP 403 + 'error code 1010'. Add a browser-like User-Agent header
to the request.

The onboarding wizard's 'Send Test Message' button (and clock-in/out
push messages) now succeed.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

utils/discord_webhook.py

@@ -10,6 +10,10 @@ import urllib.error
 from datetime import datetime
 from typing import Optional, List
 
+# Discord/Cloudflare는 Python 기본 UA(Python-urllib/3.x)를 봇으로 차단(error 1010).
+# 일반 브라우저 UA로 위장해야 통과.
+USER_AGENT = 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) ClockOutCalculator/2.3'
+
 # Discord embed 색상 (decimal)
 COLOR_GREEN = 0x57F287
 COLOR_BLUE = 0x5865F2
@@ -49,7 +53,10 @@ def send(webhook_url: str, title: str, description: str,
     data = json.dumps(payload, ensure_ascii=False).encode('utf-8')
     req = urllib.request.Request(
         webhook_url, data=data,
-        headers={'Content-Type': 'application/json; charset=utf-8'},
+        headers={
+            'Content-Type': 'application/json; charset=utf-8',
+            'User-Agent': USER_AGENT,
+        },
         method='POST',
     )
     try: