Partner promo codes: reusable codes that add free ad credits, tracked per redemption

promos.js (promo_codes + promo_redemptions, JSON fallback): create/update codes with
credits, partner, optional cap and expiry, on/off. Redeemed once per account either
from a join link ?promo=CODE (cookie, applied at signup) or the Overview box
'Have a promo code?' (/api/my/promo/redeem). Admin > Traffic gets a Partner promo
codes card (create, toggle, uses, recent redemptions). Chatbot line added.

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

public/my.html

@@ -258,6 +258,10 @@
             </div>
             <div class="card"><h3>Earning levels</h3>
               <p id="qualLine" class="muted small">…</p></div>
+            <div class="card" id="promoCard"><h3>Have a promo code?</h3>
+              <p class="muted small" style="margin:6px 0 10px">Codes from partner sites add free ad credits to your account. One use per code.</p>
+              <div style="display:flex;gap:8px;flex-wrap:wrap"><input id="promoCode" type="text" placeholder="CODE" autocomplete="off" style="flex:1;min-width:140px;text-transform:uppercase"><button type="button" class="btn small" id="promoApply">Apply</button></div>
+              <p class="small" id="promoMsg" hidden style="margin:8px 0 0"></p></div>
           </div>
         </div>
         <div class="card" id="adSlotOverview" hidden></div>
@@ -911,7 +915,7 @@
 <script src="/assets/common.js?v=20260912b"></script>
 <script src="/assets/wallet.js?v=20260911a"></script>
 <script src="/assets/promo.js?v=20260911a"></script>
-<script src="/assets/my.js?v=20260912b"></script>
+<script src="/assets/my.js?v=20260912c"></script>
 <script src="/assets/chat.js?v=20260907l"></script>
 </body>
 </html>