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/rollup/dist/shared/fsevents-importer.js

@@ -0,0 +1,37 @@
+/*
+  @license
+	Rollup.js v4.62.2
+	Fri, 19 Jun 2026 14:55:11 GMT - commit 8faa18777374582bb813d54ce3623f4acf1f9e0b
+
+	https://github.com/rollup/rollup
+
+	Released under the MIT License.
+*/
+'use strict';
+
+let fsEvents;
+let fsEventsImportError;
+async function loadFsEvents() {
+    try {
+        ({ default: fsEvents } = await import('fsevents'));
+    }
+    catch (error) {
+        fsEventsImportError = error;
+    }
+}
+// A call to this function will be injected into the chokidar code
+function getFsEvents() {
+    if (fsEventsImportError)
+        throw fsEventsImportError;
+    return fsEvents;
+}
+
+const fseventsImporter = /*#__PURE__*/Object.defineProperty({
+    __proto__: null,
+    getFsEvents,
+    loadFsEvents
+}, Symbol.toStringTag, { value: 'Module' });
+
+exports.fseventsImporter = fseventsImporter;
+exports.loadFsEvents = loadFsEvents;
+//# sourceMappingURL=fsevents-importer.js.map