refactor: clean up try_cache defaults and add SWR to sponsorship loaders

- Remove vestigial try_cache param from generate_qr_code (never used in body)
- Remove vestigial try_cache from ae_core_functions: load_ae_obj_id__site_domain,
  update_ae_obj_id_crud, update_ae_obj_id_crud_v2 (none referenced it in body)
- Add proper SWR pattern to load_ae_obj_id__sponsorship_cfg and
  load_ae_obj_id__sponsorship; change defaults from false to true
- Change load_ae_obj_id__event_file default try_cache from false to true
  (consistent with load_ae_obj_li__event_file)
- Change load_ae_obj_id__hosted_file default try_cache from false to true
  (consistent with load_ae_obj_li__hosted_file)
- Remove stale try_cache arg from element_ae_crud.svelte caller

src/lib/ae_events/ae_events__event_file.ts

@@ -13,7 +13,7 @@ export async function load_ae_obj_id__event_file({
     event_file_id,
     inc_hosted_file = false,
     view = 'default',
-    try_cache = false,
+    try_cache = true,
     log_lvl = 0
 }: {
     api_cfg: any;