feat(sync): persist polling intervals across all Launcher variants

- Migrated background timers to persistent 'sync_intervals' store.\n- Updated Sync Monitor and Config UI to display and edit all six polling loops.\n- Ensured timer settings are applied and persisted regardless of native mode status.\n- Refined initialization logic to prioritize user configuration with robust fallbacks.

src/lib/stores/ae_events_stores.ts

@@ -167,6 +167,16 @@ const events_local_data_struct: key_val = {
         time_format: 'time_12_short',
         time_hours: 12, // 12 or 24
 
+        sync_intervals: {
+            event: 90000,
+            device: 60000,
+            location: 30000,
+            session: 15000,
+            presentation: 45000,
+            presenter: 60000,
+            file_sync: 10000
+        },
+
         slct: {
             event_id: null,
             event_location_id: null,