fix(launcher): add sync pause toggle and reduce default polling intervals

The SWR pattern always fires a background API call on cache hits, so the
15s session interval created a continuous API stream even when data was
fresh. Increased all defaults: session 15s->60s, location/device 30s->60s,
presentation/presenter 45-60s->120s.

Added sync_paused guard to all six refresh functions and a Pause/Resume
toggle in the Sync Timers config section (visible without edit mode) so
testing and troubleshooting don't require a full reload.

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

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

@@ -18,6 +18,26 @@
         2} | Loops: Active"
 >
     <!-- Content omitted for brevity, preserved in file -->
+    <!-- Pause toggle: always visible — useful during testing or onsite troubleshooting -->
+    <div class="flex items-center justify-between mb-2 p-2 rounded border border-surface-500/10 bg-surface-500/5">
+        <span class="text-[10px] font-bold uppercase tracking-wider opacity-70">
+            {$events_loc.launcher.sync_paused ? '⏸ Sync Paused' : '▶ Sync Active'}
+        </span>
+        <button
+            type="button"
+            onclick={() => ($events_loc.launcher.sync_paused = !$events_loc.launcher.sync_paused)}
+            class="btn btn-xs transition-all"
+            class:preset-tonal-warning={$events_loc.launcher.sync_paused}
+            class:preset-tonal-success={!$events_loc.launcher.sync_paused}
+        >
+            {#if $events_loc.launcher.sync_paused}
+                <span class="fas fa-play mr-1"></span> Resume
+            {:else}
+                <span class="fas fa-pause mr-1"></span> Pause
+            {/if}
+        </button>
+    </div>
+
     {#if $events_loc.launcher.sync_intervals}
         <div class="grid grid-cols-1 gap-3">
             <!-- Technical Timers (Edit Mode Only) -->

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

@@ -21,13 +21,16 @@
     let last_heartbeat: string | null = $state(null);
 
     // Loop Timings (Visible in UI)
+    // WHY: Session was 15s which combined with the SWR background-refresh pattern
+    // caused a continuous API call every 15s even on cache hits. 60s is still
+    // responsive for live conference use but dramatically reduces server load.
     let loop_info = $state({
         event: 90000,
         device: 60000,
-        location: 30000,
-        session: 15000,
-        presentation: 45000,
-        presenter: 60000
+        location: 60000,
+        session: 60000,
+        presentation: 120000,
+        presenter: 120000
     });
 
     // Timer Handles
@@ -116,6 +119,7 @@
      * API Refresh: Event
      */
     async function refresh_event_data() {
+        if ($events_loc.launcher.sync_paused) return;
         if (!$events_slct.event_id) return;
         try {
             await events_func.load_ae_obj_id__event({
@@ -134,6 +138,7 @@
      * API Refresh: Sessions in Room
      */
     async function refresh_session_data() {
+        if ($events_loc.launcher.sync_paused) return;
         const location_id = $events_slct.event_location_id;
         if (!location_id) return;
         try {
@@ -153,6 +158,7 @@
      * API Refresh: Presentations for Selected Session
      */
     async function refresh_presentation_data() {
+        if ($events_loc.launcher.sync_paused) return;
         const session_id = $events_slct.event_session_id;
         if (!session_id) return;
         try {
@@ -171,6 +177,7 @@
      * API Refresh: Presenters for Selected Session
      */
     async function refresh_presenter_data() {
+        if ($events_loc.launcher.sync_paused) return;
         const session_id = $events_slct.event_session_id;
         if (!session_id) return;
         try {
@@ -186,6 +193,7 @@
     }
 
     async function run_sync_cycle() {
+        if ($events_loc.launcher.sync_paused) return;
         const location_id = $events_slct.event_location_id;
         const cache_root = $ae_loc.local_file_cache_path;
         const prefix_len = $ae_loc.native_device?.hash_prefix_length || 2;
@@ -373,6 +381,7 @@
      * Ensures we have latest room settings.
      */
     async function refresh_location_config() {
+        if ($events_loc.launcher.sync_paused) return;
         const location_id = $events_slct.event_location_id;
         if (!location_id) return;