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>

si/index.html

@@ -211,7 +211,7 @@
                     <h1>Opolnomočimo mlade z veščinami za spreminjanje sveta</h1>
                     <p>Bodi del naše razburljive poti. Pridruži se naši študentski organizaciji še danes!</p>
                 </div>
-                <a href="../si/become-a-member/" class="btn btn-primary-orange">Postani član</a>
+                <a href="../si/become-a-member/#join-form" class="btn btn-primary-orange">Postani član</a>
             </div>
         </section>
 
@@ -298,7 +298,7 @@
                         <span class="activity-tab-label">Študentsko predstavništvo</span>
                     </button>
                     </div>
-                    <a href="../si/become-a-member/" class="btn btn-primary-orange activities-cta">Postani član</a>
+                    <a href="../si/become-a-member/#join-form" class="btn btn-primary-orange activities-cta">Postani član</a>
                 </div>
                 <div class="activities-panels">
                 <div class="activity-panel active" role="tabpanel" data-panel="0">
@@ -417,7 +417,7 @@
                 <h2>Najdi svoje ljudi v Sloveniji</h2>
                 <p class="join-cta-lead">Spoznaj ljudi, obišči dogodke, dobi podporo, ustvarjaj projekte in postani del makedonske študentske skupnosti po vsej Sloveniji.</p>
                 <div class="join-cta-actions">
-                    <a class="btn btn-primary-orange" href="../si/become-a-member/">Postani član</a>
+                    <a class="btn btn-primary-orange" href="../si/become-a-member/#join-form">Postani član</a>
                     <a class="btn btn-secondary" href="../si/projects/">Poglej, kaj počnemo</a>
                 </div>
             </div>