portico: Point Zulip logo to zulip.com for self-hosters.

templates/zerver/portico-header.html

@@ -5,7 +5,7 @@
             <a class="brand logo" href="{{ root_domain_url }}/"><img draggable="false" src="{{ custom_logo_url }}" class="portico-logo" alt="{{ _('Zulip') }}" content="Zulip" /></a>
             {% else %}
             <div class="brand logo">
-                <a href="{{ root_domain_url }}/">
+                <a href="{% if is_self_hosting_management_page %}https://zulip.com/{% else %}{{ root_domain_url }}/{% endif %}">
                     <svg class="brand-logo" role="img" aria-label="{{ _('Zulip') }}" xmlns="http://www.w3.org/2000/svg" viewBox="68.96 55.62 1742.12 450.43" height="25">
                         <path fill="hsl(0, 0%, 27%)" d="M473.09 122.97c0 22.69-10.19 42.85-25.72 55.08L296.61 312.69c-2.8 2.4-6.44-1.47-4.42-4.7l55.3-110.72c1.55-3.1-.46-6.91-3.64-6.91H129.36c-33.22 0-60.4-30.32-60.4-67.37 0-37.06 27.18-67.37 60.4-67.37h283.33c33.22-.02 60.4 30.3 60.4 67.35zM129.36 506.05h283.33c33.22 0 60.4-30.32 60.4-67.37 0-37.06-27.18-67.37-60.4-67.37H198.2c-3.18 0-5.19-3.81-3.64-6.91l55.3-110.72c2.02-3.23-1.62-7.1-4.42-4.7L94.68 383.6c-15.53 12.22-25.72 32.39-25.72 55.08 0 37.05 27.18 67.37 60.4 67.37zm522.5-124.15l124.78-179.6v-1.56H663.52v-48.98h190.09v34.21L731.55 363.24v1.56h124.01v48.98h-203.7V381.9zm338.98-230.14V302.6c0 45.09 17.1 68.03 47.43 68.03 31.1 0 48.2-21.77 48.2-68.03V151.76h59.09V298.7c0 80.86-40.82 119.34-109.24 119.34-66.09 0-104.96-36.54-104.96-120.12V151.76h59.48zm244.91 0h59.48v212.25h104.18v49.76h-163.66V151.76zm297 0v262.01h-59.48V151.76h59.48zm90.18 3.5c18.27-3.11 43.93-5.44 80.08-5.44 36.54 0 62.59 7 80.08 20.99 16.72 13.22 27.99 34.99 27.99 60.64 0 25.66-8.55 47.43-24.1 62.2-20.21 19.05-50.15 27.6-85.13 27.6-7.77 0-14.77-.39-20.21-1.17v93.69h-58.7V155.26zm58.7 118.96c5.05 1.17 11.27 1.55 19.83 1.55 31.49 0 50.92-15.94 50.92-42.76 0-24.1-16.72-38.49-46.26-38.49-12.05 0-20.21 1.17-24.49 2.33v77.37z"/>
                     </svg>