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/@babel/runtime/helpers/esm/get.js

@@ -0,0 +1,11 @@
+import superPropBase from "./superPropBase.js";
+function _get() {
+  return _get = "undefined" != typeof Reflect && Reflect.get ? Reflect.get.bind() : function (e, t, r) {
+    var p = superPropBase(e, t);
+    if (p) {
+      var n = Object.getOwnPropertyDescriptor(p, t);
+      return n.get ? n.get.call(arguments.length < 3 ? e : r) : n.value;
+    }
+  }, _get.apply(null, arguments);
+}
+export { _get as default };