Add "Manage cookies" footer link (GDPR consent withdrawal)

Adds a per-language "Manage cookies" link to the footer legal bar on all
201 pages, wired to window.msosOpenConsent() so visitors can change or
withdraw their choice at any time (GDPR requirement). Verified: decline ->
re-open via link -> accept flips analytics consent to granted.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

en/become-a-member/index.html

@@ -591,6 +591,7 @@
             <div class="legal-links">
                 <a href="../../en/privacy-policy/">Privacy policy</a>
                 <a href="../../en/cookie-policy/">Cookie policy</a>
+                <a href="#" class="js-manage-cookies" onclick="if(window.msosOpenConsent){msosOpenConsent();}return false;">Manage cookies</a>
             </div>
         </div>
     </div>