Add sync error logging, extend error flash, fix unload saves

- Log workforce sync errors to backend stdout so they appear in docker logs
- Extend error flash from 5s to 15s so errors are readable
- Replace sendBeacon (POST-only) with keepalive fetch (PUT) on unload —
  sendBeacon was hitting 404s on all three unload saves

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

frontend/node_modules/workbox-core/setCacheNameDetails.d.ts

@@ -0,0 +1,21 @@
+import { PartialCacheNameDetails } from './_private/cacheNames.js';
+import './_version.js';
+/**
+ * Modifies the default cache names used by the Workbox packages.
+ * Cache names are generated as `<prefix>-<Cache Name>-<suffix>`.
+ *
+ * @param {Object} details
+ * @param {Object} [details.prefix] The string to add to the beginning of
+ *     the precache and runtime cache names.
+ * @param {Object} [details.suffix] The string to add to the end of
+ *     the precache and runtime cache names.
+ * @param {Object} [details.precache] The cache name to use for precache
+ *     caching.
+ * @param {Object} [details.runtime] The cache name to use for runtime caching.
+ * @param {Object} [details.googleAnalytics] The cache name to use for
+ *     `workbox-google-analytics` caching.
+ *
+ * @memberof workbox-core
+ */
+declare function setCacheNameDetails(details: PartialCacheNameDetails): void;
+export { setCacheNameDetails };