feat: persist exact Week Ahead task times (Closes #1270)

frontend/index.html

@@ -593,6 +593,7 @@
       <div class="small week-calendar-status" id="week-calendar-status" role="status" aria-live="assertive"></div>
       <div class="week-calendar-actions">
         <button id="back-to-week-review-from-calendar" type="button">Back to review</button>
+        <button id="save-week-calendar-times" type="button">Save exact times</button>
         <button id="share-week-calendar" type="button">Share calendar blocks</button>
       </div>
     </section>