fix: restore missing {% else %} in step3 tink_link_url template block

Sandbox note edit accidentally removed the {% else %} tag, causing the
entire bank connection UI (sandbox note + Åbn Tink Link button) to only
render when cb_success=True — i.e. never shown before connecting.

src/templates/step.html

@@ -114,6 +114,7 @@
       </div>
     </div>
 
+    {% else %}
     <!-- Not yet connected — show connection UI -->
 
     <!-- Sandbox note: anonymous flow vs production -->