feat: batch-defer mobile search results (Closes #813)

frontend/index.html

@@ -458,6 +458,7 @@
   <div class="search-batch-actions" id="search-batch-actions" hidden>
     <span id="search-selection-status" class="small" aria-live="polite">No issues selected.</span>
     <button id="cancel-search-selection" type="button">Cancel</button>
+    <button id="defer-selected-search-results" type="button" disabled>Defer</button>
     <button id="queue-selected-search-results" type="button" disabled>Assign &amp; add to Today</button>
   </div>
   <section class="search-batch-estimate-review" id="search-batch-estimate-review"