feat: notify pending Human Gate decisions (Closes #1437)

frontend/index.html

@@ -233,6 +233,8 @@
             <button class="secondary" id="push-test" type="button" hidden>Send test notification</button>
             <label class="push-update-control" for="push-following"><input id="push-following" type="checkbox" /> Notify me when Following changes</label>
             <span class="small" id="push-following-status" role="status" aria-live="polite"></span>
+            <label class="push-update-control" for="push-human-gates"><input id="push-human-gates" type="checkbox" /> Notify me when release decisions are waiting</label>
+            <span class="small" id="push-human-gates-status" role="status" aria-live="polite"></span>
             <label class="push-update-control" for="push-quiet-hours"><input id="push-quiet-hours" type="checkbox" /> Pause routine alerts on a schedule</label>
             <div class="push-quiet-hours-times">
               <label for="push-quiet-start">From <input id="push-quiet-start" type="time" value="22:00" /></label>