Add export button for channel data and update API integration

Co-authored-by: Copilot <copilot@github.com>

webui/index.html

@@ -194,8 +194,7 @@
         <td class="last-date"></td>
         <td>
           <div class="action-row">
-            <button class="button button-small scrape-btn">Scrape</button>
-            <button class="button button-small export-view-btn">Viewer</button>
+            <button class="button button-small scrape-btn">Scrape</button>            <button class="button button-small export-btn">Export</button>            <button class="button button-small export-view-btn">Viewer</button>
             <button class="button button-small media-btn">Rescrape media</button>
             <button class="button button-small danger remove-btn">Удалить</button>
           </div>