Clarify server nav labels (Default Server Interface vs All Servers)

No route/logic changes - pure label cleanup so the legacy default-server
editor and the multi-server management page are no longer confusable.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

templates/base.html

@@ -132,7 +132,7 @@
                             <a href="{{.basePath}}/wg-server" class="nav-link {{if eq .baseData.Active "wg-server" }}active{{end}}">
                                 <i class="nav-icon fas fa-server"></i>
                                 <p>
-                                    Wireguard Server
+                                    Default Server Interface
                                 </p>
                             </a>
                         </li>
@@ -143,7 +143,7 @@
                             <a href="{{.basePath}}/servers-settings" class="nav-link {{if eq .baseData.Active "servers" }}active{{end}}">
                                 <i class="nav-icon fas fa-server"></i>
                                 <p>
-                                    Servers
+                                    All Servers
                                 </p>
                             </a>
                         </li>