Implement auto-prefill for Exhibitor shared passcode for trusted users

src/routes/events/[event_id]/(leads)/leads/exhibit/[exhibit_id]/ae_comp__exhibit_signin.svelte

@@ -6,6 +6,7 @@
     import { page } from '$app/state';
     import { liveQuery } from 'dexie';
     import { db_events } from '$lib/ae_events/db_events';
+    import { ae_loc } from '$lib/stores/ae_stores';
     import { events_loc, events_sess } from '$lib/stores/ae_events_stores';
     import { Key, Mail, Lock, User, ArrowRight, LoaderCircle, AlertCircle, CheckCircle2 } from 'lucide-svelte';
     import { untrack } from 'svelte';
@@ -27,6 +28,15 @@
     let status = $state('idle'); // 'idle', 'submitting', 'error', 'success'
     let error_msg = $state('');
 
+    // --- Auto-prefill for Trusted Users ---
+    $effect(() => {
+        if ($ae_loc.trusted_access && $lq__exhibit_obj?.staff_passcode) {
+            untrack(() => {
+                if (!passcode) passcode = $lq__exhibit_obj?.staff_passcode ?? '';
+            });
+        }
+    });
+
     async function handle_signin() {
         if (!$lq__exhibit_obj) return;
         status = 'submitting';