pres_mgmt config: remove legacy launcher option, add back button + dirty state to config UI

- Remove show__launcher_link_legacy from PressMgmtRemoteCfg, PresMgmtLocState, and
  pres_mgmt_loc_defaults — the Flask/legacy launcher is retired
- Sync function now hardcodes hide__launcher_link_legacy=true (always hidden)
- Config page: back button to pres_mgmt, save buttons disabled until changes made
- Fix {#each} key expressions in config page
- Migrate e_app_access_type and element_manage_event_file_li to pres_mgmt_loc store
- Add temporary svelte type augments file (src/types/)

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

src/lib/ae_events/ae_events__event.ts

@@ -1050,8 +1050,8 @@ export function sync_config__event_pres_mgmt({
         // Launcher links (show__ in remote → invert to hide__ in local display state)
         loc.hide__launcher_link =
             !(pres_mgmt_cfg_remote?.show__launcher_link ?? false);
-        loc.hide__launcher_link_legacy =
-            !(pres_mgmt_cfg_remote?.show__launcher_link_legacy ?? false);
+        // Legacy Flask launcher is retired — always hide regardless of remote config
+        loc.hide__launcher_link_legacy = true;
 
         // Navigation / UI constraints
         loc.limit__navigation =