feat: configure deadline reminder horizon (Closes #727)

frontend/index.html

@@ -87,6 +87,8 @@
         <div class="device-setup-deadline-controls">
           <label for="device-setup-deadline-hour">Local hour</label>
           <select id="device-setup-deadline-hour" aria-label="Deadline reminder local hour"></select>
+          <label for="device-setup-deadline-days">Warn me</label>
+          <select id="device-setup-deadline-days" aria-label="Deadline reminder horizon"><option value="0">Due today</option><option value="2" selected>Next 2 days</option><option value="7">Next 7 days</option></select>
           <button class="device-setup-action" id="device-setup-deadline" type="button">Enable</button>
         </div>
       </li>
@@ -139,6 +141,7 @@
             <span class="small" id="push-update-status" role="status" aria-live="polite"></span>
             <label class="push-update-control" for="push-deadlines"><input id="push-deadlines" type="checkbox" /> Notify me about deadlines</label>
             <label for="push-deadline-hour">Reminder hour <select id="push-deadline-hour" aria-label="Deadline reminder local hour"></select></label>
+            <label for="push-deadline-days">Warn me <select id="push-deadline-days" aria-label="Deadline reminder horizon"><option value="0">Due today</option><option value="2" selected>Next 2 days</option><option value="7">Next 7 days</option></select></label>
             <span class="small" id="push-deadline-status" role="status" aria-live="polite"></span>
             <button id="clear-offline-work" type="button">Clear offline work data</button>
             <button id="retry-offline-storage" type="button" hidden>Retry offline saving</button>