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/es.json

@@ -5590,6 +5590,10 @@
     "webhookUrlHint": "La URL completa para el POST. Debe ser accesible públicamente.",
     "webhookHeaderName": "Nombre de cabecera (opcional)",
     "webhookHeaderValue": "Valor de cabecera (opcional)",
+    "webhookFormat": "Formato del mensaje",
+    "webhookFormatGeneric": "JSON genérico",
+    "webhookFormatGotify": "Gotify",
+    "webhookFormatGotifyHint": "Usa la URL que termina en /message y pon el token de la aplicación en la cabecera X-Gotify-Key.",
     "email": "Correo electrónico",
     "emailDescription": "Recibe alertas y recordatorios por correo electrónico.",
     "emailEnable": "Activar correo electrónico",