feat(notifications): add a Gotify payload format to the webhook

Gotify's POST /message types priority as an integer, so the generic body, which sends the word, was refused with a 400 before the token was ever the question. The webhook card now offers a payload format: generic, which stays byte for byte what it was, and gotify, which sends title, message, an integer priority and extras.

Priorities follow the Gotify Android client's channel thresholds: 5 for routine events (audible), 8 for medication reminders (the lowest heads-up value), 10 for urgent events. The extras declare plain text and carry the event name, masked to reminder in discreet mode as the generic body does.

The choice lives in the encrypted channel config, so no migration: an absent format is generic, only gotify is written, and a save that omits the field keeps the stored choice. GET returns the resolved value. The sender comment no longer suggests an Authorization Bearer header for Gotify, which takes X-Gotify-Key or a token query parameter.

Refs #947

messages/ko.json

@@ -5590,6 +5590,10 @@
     "webhookUrlHint": "POST를 보낼 전체 URL이에요. 외부에서 접근할 수 있어야 해요.",
     "webhookHeaderName": "헤더 이름 (선택)",
     "webhookHeaderValue": "헤더 값 (선택)",
+    "webhookFormat": "메시지 형식",
+    "webhookFormatGeneric": "일반 JSON",
+    "webhookFormatGotify": "Gotify",
+    "webhookFormatGotifyHint": "/message로 끝나는 URL을 쓰고, 앱 토큰은 X-Gotify-Key 헤더에 넣어 주세요.",
     "email": "이메일",
     "emailDescription": "경고와 알림을 이메일로 받아요.",
     "emailEnable": "이메일 켜기",