Link "Become a member" CTAs directly to the signup form

Every body CTA (hero buttons, join-cta sections, article sidebars,
activities CTA) now points to become-a-member/#join-form so a click
lands on the form instead of the top of the page. The header menu
tab (btn-secondary) is intentionally left pointing at the page root.

93 links across 45 pages (en/mk/si). HTML-only, self-templated build
preserves the sidebar CTAs, so no rebuild/cache-bust needed.

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

en/projects/joint-walk-path-around-the-wire/index.html

@@ -222,7 +222,7 @@
                 </nav>
                 <div class="sidebar-cta">
                     <p class="sidebar-cta-title">Like what we do?</p>
-                    <a class="sidebar-cta-btn" href="../../../en/become-a-member/">Become a member</a>
+                    <a class="sidebar-cta-btn" href="../../../en/become-a-member/#join-form">Become a member</a>
                     <p class="sidebar-cta-note">Or <a href="../../../en/support/">support MSOS</a> so we can create even more moments like this.</p>
                 </div>
             </aside>
@@ -288,7 +288,7 @@
                 <h3>Like what we do?</h3>
                 <p>Become a member or support MSOS so we can create even more moments like this.</p>
                 <div class="asc-actions">
-                    <a class="btn btn-primary-orange" href="../../../en/become-a-member/">Become a member</a>
+                    <a class="btn btn-primary-orange" href="../../../en/become-a-member/#join-form">Become a member</a>
                     <a class="btn btn-secondary" href="../../../en/support/">Support MSOS</a>
                 </div>
             </div>