fix(launcher): skip url files in sync

src/routes/events/[event_id]/(launcher)/launcher_background_sync.svelte

@@ -24,6 +24,16 @@ let sync_results: Record<string, 'success' | 'error' | 'pending'> = $state({});
 let sync_stats = $state({ total: 0, cached: 0, missing: 0 });
 let last_heartbeat: string | null = $state(null);
 
+function is_url_file(file_obj: any): boolean {
+    const filename = (file_obj?.filename ?? '') as string;
+    const extension = (file_obj?.extension ?? '').toLowerCase();
+    return (
+        filename.startsWith('https://') ||
+        filename.startsWith('http://') ||
+        extension === 'url'
+    );
+}
+
 // Loop Timings (Visible in UI)
 // WHY: Session was originally 15s which combined with the SWR background-refresh
 // pattern caused a continuous API call every 15s even on cache hits. 60s is still
@@ -294,11 +304,13 @@ async function run_sync_cycle() {
             .anyOf(all_for_ids)
             .toArray();
 
-        sync_stats.total = files.length;
+        const cacheable_files = files.filter((file_obj) => !is_url_file(file_obj));
+
+        sync_stats.total = cacheable_files.length;
         let cached_count = 0;
         let missing_count = 0;
 
-        for (const file_obj of files) {
+        for (const file_obj of cacheable_files) {
             // Re-check pause flag each iteration — a sync cycle can run for many
             // seconds if there are missing files, so we must honour a pause request
             // mid-loop rather than waiting for the entire batch to finish.

src/routes/events/[event_id]/(launcher)/launcher_file_cont.svelte

@@ -110,7 +110,8 @@ let is_online: boolean = $state(typeof navigator !== 'undefined' ? navigator.onL
  */
 const is_url = $derived(
     (event_file_obj?.filename ?? '').startsWith('https://') ||
-    (event_file_obj?.filename ?? '').startsWith('http://')
+    (event_file_obj?.filename ?? '').startsWith('http://') ||
+    (event_file_obj?.extension ?? '').toLowerCase() === 'url'
 );
 
 let screen_saver_exts = ['jpg', 'png', 'PNG', 'webp'];