refactor: rename ae_hide_menu URL param to hide_menu

ae_ prefix belongs on Svelte component/variable names, not URL params.
Updated both the consumer (+layout.svelte) and the builder (jitsi_url_builder).

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/routes/+layout.svelte

@@ -254,10 +254,10 @@
         if (iframe === 'true') $ae_loc.iframe = true;
         else if (iframe === 'false') $ae_loc.iframe = false;
 
-        // ae_hide_menu=true — suppress the AE system bar when embedding in Novi or
+        // hide_menu=true — suppress the AE system bar when embedding in Novi or
         // other host pages with their own navigation. Applies even for trusted_access
         // users who would otherwise always see the menu in iframe mode.
-        if (data.url.searchParams.get('ae_hide_menu') === 'true') {
+        if (data.url.searchParams.get('hide_menu') === 'true') {
             $ae_loc.sys_menu.hide = true;
         }