Featured links: Extend run (book more days) replaces Buy more views; visit packs top up by visits; campaign rows say paid up front and runs through

Hugh and Michael both added credits to a featured run expecting more days. Featured is a flat
daily buy, so the credits sat unspent until the run ended and their balance read 0 meanwhile.
Now: /api/my/campaigns/:id/extend books extra days after the current run (or from today if it
ended) and charges them at once; top-up refuses featured; a visits top-up buys more visits at the
pack rate, charged now; rows show paid up front + day count + runs through <date> / run ended;
explainer under the campaign table; chatbot canned answer + AI prompt updated; my.js v tag bumped.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

public/my.html

@@ -1021,7 +1021,7 @@
 <script src="/assets/common.js?v=20260914a"></script>
 <script src="/assets/wallet.js?v=20260911a"></script>
 <script src="/assets/promo.js?v=20260911a"></script>
-<script src="/assets/my.js?v=20260915f"></script>
+<script src="/assets/my.js?v=20260916a"></script>
 <script src="/assets/chat.js?v=20260907l"></script>
 </body>
 </html>