feat: report Today blockers and move on (Closes #1066)

frontend/index.html

@@ -1601,6 +1601,13 @@
       </div>
     </section>
     <p class="small muted">Save privately on this device, or post to the exact Gitea item. Today keeps running either way.</p>
+    <section class="today-progress-blocker" aria-labelledby="today-progress-blocker-title">
+      <strong id="today-progress-blocker-title">Blocked?</strong>
+      <label for="today-blocker-return-at">Return this item to Later at</label>
+      <input id="today-blocker-return-at" type="datetime-local" />
+      <button id="post-today-blocker" type="button">Post blocker &amp; move on</button>
+      <p class="small muted">Posts this update first, then defers the item and continues Today.</p>
+    </section>
     <p id="today-progress-status" class="small" role="status" aria-live="polite"></p>
     <div class="today-progress-actions">
       <button id="save-today-progress" type="button">Save to this item</button>