Fix: Restore Native caching business logic and implement 3-mode launcher

- Implemented Default, Onsite, and Native launcher modes in launcher_file_cont.svelte.
- Restored background pre-caching logic with configurable timers in new LauncherBackgroundSync component.
- Fixed standard browser download regression for regular website mode.
- Modernized electron_relay to TypeScript and standardized bridge detection in layout.
- Detailed startup and background sync technical flow in documentation.

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

@@ -0,0 +1,126 @@
+<script lang="ts">
+    /**
+     * launcher_background_sync.svelte
+     * Handles background pre-caching of event files when running in Native mode.
+     * Uses configurable timers from the device configuration.
+     */
+    import { onMount, untrack, onDestroy } from 'svelte';
+    import { ae_loc, ae_api } from '$lib/stores/ae_stores';
+    import { events_slct } from '$lib/stores/ae_events_stores';
+    import { db_events } from '$lib/ae_events/db_events';
+    import * as native from '$lib/electron/electron_relay';
+
+    let { log_lvl = 0 } = $props();
+
+    let currently_syncing: string | null = $state(null);
+    let sync_results: Record<string, 'success' | 'error' | 'pending'> = $state({});
+    let sync_interval: any = null;
+
+    // Trigger initial sync and setup interval
+    onMount(() => {
+        if (!$ae_loc.is_native) return;
+
+        // 1. Initial Immediate Sync
+        setTimeout(() => {
+            if (log_lvl) console.log('Sync: Triggering immediate startup sync cycle.');
+            const files = $events_slct.event_file_obj_li;
+            if (files && files.length > 0) {
+                const ids = files.map((f: any) => f.event_file_id);
+                process_sync_queue(ids);
+            }
+        }, 1000);
+
+        // 2. Setup Loop Timer
+        // Default to 60 seconds if not specified in native_device config
+        const loop_period = $ae_loc.native_device?.check_event_loop_period || 60000;
+        if (log_lvl) console.log(`Sync: Starting background loop with period: ${loop_period}ms`);
+        
+        sync_interval = setInterval(() => {
+            const files = $events_slct.event_file_obj_li;
+            if (files && files.length > 0) {
+                const ids = files.map((f: any) => f.event_file_id);
+                process_sync_queue(ids);
+            }
+        }, loop_period);
+    });
+
+    onDestroy(() => {
+        if (sync_interval) clearInterval(sync_interval);
+    });
+
+    // Reactive Watch: Also trigger if the file list changes significantly
+    $effect(() => {
+        if (!$ae_loc.is_native) return;
+        
+        const files = $events_slct.event_file_obj_li;
+        if (!files || files.length === 0) return;
+
+        untrack(() => {
+            const file_ids = files.map((f: any) => f.event_file_id);
+            // Only process if we haven't checked these specific IDs recently
+            process_sync_queue(file_ids);
+        });
+    });
+
+    /**
+     * Iterates through the file list and downloads missing files.
+     */
+    async function process_sync_queue(ids: string[]) {
+        const cacheRoot = $ae_loc.local_file_cache_path;
+        if (!cacheRoot) {
+            console.warn('Sync: local_file_cache_path not set. Skipping sync.');
+            return;
+        }
+
+        if (log_lvl) console.log(`Sync: Processing queue of ${ids.length} files...`);
+
+        for (const id of ids) {
+            // Skip if already successfully cached in this session to avoid redundant IPC calls
+            if (sync_results[id] === 'success') continue;
+
+            try {
+                const file_obj = await db_events.file.get(id);
+                if (!file_obj || !file_obj.hash_sha256) continue;
+
+                const exists = await native.check_hash_file_cache({ 
+                    cacheRoot, 
+                    hash: file_obj.hash_sha256 
+                });
+
+                if (exists) {
+                    sync_results[id] = 'success';
+                    continue;
+                }
+
+                if (log_lvl) console.log(`Sync: Downloading missing file: ${file_obj.filename}`);
+                currently_syncing = file_obj.filename;
+                
+                const url = `${$ae_api.base_url}/v3/crud/hosted_file/${file_obj.hosted_file_id}/download`;
+                const result = await native.download_to_cache({
+                    url,
+                    cacheRoot,
+                    hash: file_obj.hash_sha256,
+                    apiKey: $ae_api.api_secret_key
+                });
+
+                if (result.success) {
+                    sync_results[id] = 'success';
+                    if (log_lvl) console.log(`Sync: Successfully cached ${file_obj.filename}`);
+                } else {
+                    console.error(`Sync: Failed to cache ${file_obj.filename}:`, result.error);
+                    sync_results[id] = 'error';
+                }
+            } catch (err) {
+                console.error(`Sync: Error processing file ${id}:`, err);
+            }
+        }
+        currently_syncing = null;
+    }
+</script>
+
+{#if currently_syncing && log_lvl}
+    <div class="fixed bottom-4 right-4 bg-black/80 text-white p-2 rounded-lg text-[10px] z-[9999] border border-primary-500 animate-pulse">
+        <span class="fas fa-sync fa-spin mr-2"></span>
+        Pre-Caching: {currently_syncing}
+    </div>
+{/if}