feat(launcher): configurable .tmp cache cleanup in cfg panel

- launcher_cfg_local_actions.svelte: add "Cache Maintenance" block
  (native-only, gated by is_native && cache_root); number input for
  max age in hours, "Clean Now" button with status feedback
- launcher_background_sync.svelte: read cleanup_tmp_max_age_hours
  from events_loc.launcher store (default 24h) instead of hardcoded
  1440 minutes; setting persists across sessions via persisted store

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

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

@@ -1,6 +1,7 @@
 <script lang="ts">
     import { ae_loc, ae_api } from '$lib/stores/ae_stores';
     import { events_loc } from '$lib/stores/ae_events_stores';
+    import { cleanup_tmp_files } from '$lib/electron/electron_relay';
     import Launcher_Cfg_Section from './launcher_cfg_section.svelte';
 
     interface Props {
@@ -9,6 +10,17 @@
     let { on_expand }: Props = $props();
 
     let selected_reset = $state('');
+    let cleanup_status = $state('');
+
+    async function handle_cleanup_now() {
+        const cache_root = $ae_loc.local_file_cache_path;
+        if (!cache_root) { cleanup_status = 'Error: Cache path not set.'; return; }
+        const max_age_hours = $events_loc.launcher.cleanup_tmp_max_age_hours ?? 24;
+        cleanup_status = 'Cleaning...';
+        const result = await cleanup_tmp_files({ cache_root, max_age_minutes: max_age_hours * 60 });
+        cleanup_status = (result as any).success !== false ? 'Done.' : `Error: ${(result as any).error}`;
+        setTimeout(() => (cleanup_status = ''), 4000);
+    }
 
     function handle_reset_action(val: string) {
         if (!val) return;
@@ -128,7 +140,39 @@
             </button>
         </div>
 
-        <!-- 3. Connection Summary (Edit Mode Only) -->
+        <!-- 3. Cache .tmp Cleanup (Native Only) -->
+        {#if $ae_loc.is_native && $ae_loc.local_file_cache_path}
+            <div class="flex flex-col gap-1 border-t border-surface-500/20 pt-2 mt-1">
+                <span class="text-[9px] font-bold uppercase opacity-50 ml-1">Cache Maintenance</span>
+                <div class="flex items-center gap-2">
+                    <label for="cleanup_max_age" class="text-[10px] opacity-70 whitespace-nowrap">Max age (hrs):</label>
+                    <input
+                        id="cleanup_max_age"
+                        type="number"
+                        min="1"
+                        max="168"
+                        bind:value={$events_loc.launcher.cleanup_tmp_max_age_hours}
+                        class="input input-sm w-16 h-7 text-xs text-center preset-tonal-surface"
+                        placeholder="24"
+                    />
+                    <button
+                        type="button"
+                        onclick={handle_cleanup_now}
+                        class="btn btn-xs preset-tonal-warning hover:preset-filled-warning-500 grow"
+                    >
+                        <span class="fas fa-broom mr-1"></span> Clean .tmp Now
+                    </button>
+                </div>
+                {#if cleanup_status}
+                    <span class="text-[9px] italic opacity-60 ml-1">{cleanup_status}</span>
+                {/if}
+                <span class="text-[8px] opacity-40 italic ml-1 leading-tight">
+                    Removes stale in-progress download artifacts. Auto-runs on startup.
+                </span>
+            </div>
+        {/if}
+
+        <!-- 4. Connection Summary (Edit Mode Only) -->
         {#if $ae_loc.edit_mode}
             <div
                 class="col-span-full border-t border-surface-500/20 pt-2 mt-1 flex flex-col gap-1"

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

@@ -108,11 +108,12 @@
         setTimeout(() => refresh_presentation_data(), 3000);
         setTimeout(() => refresh_presenter_data(), 5000);
 
-        // Clean up stale .tmp files (interrupted downloads) older than 24h.
-        // Run once at startup — sufficient for conference day usage.
+        // Clean up stale .tmp files (interrupted downloads) on startup.
+        // Age threshold is user-configurable (cfg → General → Cache Maintenance), default 24h.
         const cache_root = $ae_loc.local_file_cache_path;
         if ($ae_loc.is_native && cache_root) {
-            cleanup_tmp_files({ cache_root }).then((result) => {
+            const max_age_hours = $events_loc.launcher.cleanup_tmp_max_age_hours ?? 24;
+            cleanup_tmp_files({ cache_root, max_age_minutes: max_age_hours * 60 }).then((result) => {
                 if (log_lvl) console.log('Sync: .tmp cleanup complete.', result);
             });
         }