Add default-server ntfy auth (fix 403 on protected topics)

The "send test" action, admin alerts and feeds without their own
credentials now use configurable default-server token / basic auth,
so publishing works against ntfy servers with access control enabled.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

app/static/app.js

@@ -410,6 +410,9 @@ sForm.addEventListener("submit", async e => {
   e.preventDefault();
   const payload = {
     default_ntfy_server: sForm.default_ntfy_server.value.trim(),
+    default_ntfy_token: sForm.default_ntfy_token.value.trim(),
+    default_ntfy_username: sForm.default_ntfy_username.value.trim(),
+    default_ntfy_password: sForm.default_ntfy_password.value,
     check_interval: parseInt(sForm.check_interval.value, 10),
     auth_enabled: sForm.auth_enabled.checked,
     telegram_enabled: sForm.telegram_enabled.checked,

app/static/i18n.js

@@ -46,6 +46,8 @@ const I18N = {
     "settings.ntfy": "ntfy",
     "settings.defaultServer": "Сервер ntfy по умолчанию",
     "settings.defaultServerHint": "Используется для лент, у которых не задан собственный сервер.",
+    "settings.ntfyAuth": "Авторизация на сервере ntfy",
+    "settings.ntfyAuthHint": "Нужно, если на сервере включён контроль доступа (ошибка 403 при отправке). Применяется к тесту, алертам и лентам без собственной авторизации.",
     "settings.testPh": "тема для теста, напр. my-news",
     "settings.testBtn": "Отправить тест",
     "settings.check": "Проверка",
@@ -193,6 +195,8 @@ const I18N = {
     "settings.ntfy": "ntfy",
     "settings.defaultServer": "Default ntfy server",
     "settings.defaultServerHint": "Used for feeds that don't define their own server.",
+    "settings.ntfyAuth": "ntfy server authentication",
+    "settings.ntfyAuthHint": "Needed if the server has access control enabled (403 on publish). Applies to the test, alerts and feeds without their own auth.",
     "settings.testPh": "topic to test, e.g. my-news",
     "settings.testBtn": "Send test",
     "settings.check": "Polling",