feat: sync Today plan across devices (#357)

frontend/index.html

@@ -99,6 +99,7 @@
     <div class="small" id="notification-page-status" aria-live="polite"></div>
     <button class="load-more-notifications" id="load-more-notifications" type="button" hidden>Load older updates</button>
     <div class="small" id="my-work-action-status" aria-live="assertive"></div>
+    <div class="small" id="today-sync-status" aria-live="polite">Today is saved on this device.</div>
     <button class="retry-work-route" id="retry-work-route" type="button" hidden>Retry shared work item</button>
     <div class="small" id="work-route-share-status" aria-live="polite"></div>
     <div class="my-work-bulk" id="bulk-mark-read-bar" hidden>
@@ -538,6 +539,7 @@
 <script src="static/offline-today.js"></script>
 <script src="static/my-work.js"></script>
 <script src="static/today-work.js"></script>
+<script src="static/today-sync.js"></script>
 <script src="static/update-ownership.js"></script>
 <script src="static/later-work.js"></script>
 <script src="static/detail-defer.js"></script>