feat(launcher): auto-apply kiosk URL params on Launcher link for poster sessions

When on a Poster Session in Pres Mgmt, the Launcher nav link now appends
?iframe=true&launcher_menu=hide so the recipient opens a clean kiosk view
without the site header or left session panel.

- ae_comp__events_menu_nav: add events__launcher_extra_params prop; update
  launcher_sess_qry to merge extra params after session_id
- session_page_menu: derive is_poster from type_code and pass the kiosk
  params into the Launcher link

src/routes/events/ae_comp__events_menu_nav.svelte

@@ -23,6 +23,7 @@
         events__launcher_session_id?: null | string; // event_session_id to pass to launcher as ?session_id=
         events__session_id?: null | string; // event_session_id — used for "Back to Session" link only
         events__session_search?: boolean; // event_id
+        events__launcher_extra_params?: string; // extra URL params appended to the launcher link (e.g. 'iframe=true&launcher_menu=hide')
     }
 
     let {
@@ -31,6 +32,7 @@
         ae_core = false,
         events__launcher_id = null,
         events__launcher_session_id = null,
+        events__launcher_extra_params = '',
         events__location_id = null,
         events__locations = false,
         events__reports = false,
@@ -41,7 +43,12 @@
 
     // Build launcher URL segments separately so the href template stays simple (avoids ternaries in href attr)
     let launcher_loc_seg = $derived(events__launcher_id ? `/${events__launcher_id}` : '');
-    let launcher_sess_qry = $derived(events__launcher_session_id ? `?session_id=${events__launcher_session_id}` : '');
+    let launcher_sess_qry = $derived.by(() => {
+        const parts: string[] = [];
+        if (events__launcher_session_id) parts.push(`session_id=${events__launcher_session_id}`);
+        if (events__launcher_extra_params) parts.push(events__launcher_extra_params);
+        return parts.length ? `?${parts.join('&')}` : '';
+    });
 </script>
 
 <!-- This is for common navigation links. -->