Launcher: preserve legacy address fields in IDB; add file_sync to loop_info

ae_events__event.ts: Add legacy flat address fields (address_name,
address_line_1, address_city, etc.) to properties_to_save. Events
predating location_address_json still return these flat fields from
the API; they must survive an IDB round-trip without being stripped
by _process_generic_props, or the edit form's fallback reads return
undefined.

launcher_background_sync.svelte:
- Move file_sync interval into loop_info $state alongside other
  intervals; load from cfg/device config with fallback (30 s). Keeps
  all intervals in one place for UI display consistency.
- Align onMount fallback values to match loop_info defaults.
- Add sync_paused mid-loop break: long sync cycles now honour a pause
  request per-iteration rather than waiting for the entire batch.

src/lib/ae_events/ae_events__event.ts

@@ -797,7 +797,7 @@ export async function qry_ae_obj_li__event_v2({
     return filtered_obj_li.slice(0, limit);
 }
 
-// Updated 2025-05-09
+// Updated 2026-03-10
 export const properties_to_save = [
     'id',
     'event_id',
@@ -858,7 +858,23 @@ export const properties_to_save = [
     'file_count',
     'file_count_all',
     'internal_use_count',
-    'event_file_id_li_json'
+    'event_file_id_li_json',
+    // Legacy flat address fields — preserved so background SWR re-fires do not wipe
+    // address data for events that predate location_address_json.  The edit form reads
+    // these as a fallback: location_address_json?.name ?? address_name ?? ''.
+    // New saves always write structured data into location_address_json, but the API
+    // may still return the flat fields for older records and they must survive an IDB
+    // round-trip without being stripped by _process_generic_props.
+    'address_location_id',
+    'address_name',
+    'address_line_1',
+    'address_line_2',
+    'address_city',
+    'address_state',
+    'address_postal_code',
+    'address_country',
+    'address_country_alpha_2_code',
+    'address_country_subdivision_code'
 ];
 
 async function _process_generic_props<T extends Record<string, any>>({