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/templates/index.html

@@ -91,6 +91,18 @@
         <input type="text" name="default_ntfy_server" placeholder="https://ntfy.sh">
         <small class="muted" data-i18n="settings.defaultServerHint"></small>
       </label>
+      <details class="adv">
+        <summary data-i18n="settings.ntfyAuth">Авторизация на сервере ntfy</summary>
+        <label><span data-i18n="feed.token">Access token</span> <small class="muted" data-i18n="feed.tokenHint"></small>
+          <input type="text" name="default_ntfy_token" placeholder="tk_..."></label>
+        <div class="grid-2">
+          <label><span data-i18n="feed.login">Логин</span>
+            <input type="text" name="default_ntfy_username" autocomplete="off"></label>
+          <label><span data-i18n="feed.password">Пароль</span>
+            <input type="password" name="default_ntfy_password" autocomplete="new-password"></label>
+        </div>
+        <small class="muted" data-i18n="settings.ntfyAuthHint"></small>
+      </details>
       <div class="inline-test">
         <input type="text" id="test-topic" data-i18n-ph="settings.testPh">
         <button type="button" class="btn ghost" id="test-btn" data-i18n="settings.testBtn">Отправить тест</button>