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/createSuper.js

@@ -0,0 +1,16 @@
+import getPrototypeOf from "./getPrototypeOf.js";
+import isNativeReflectConstruct from "./isNativeReflectConstruct.js";
+import possibleConstructorReturn from "./possibleConstructorReturn.js";
+function _createSuper(t) {
+  var r = isNativeReflectConstruct();
+  return function () {
+    var e,
+      o = getPrototypeOf(t);
+    if (r) {
+      var s = getPrototypeOf(this).constructor;
+      e = Reflect.construct(o, arguments, s);
+    } else e = o.apply(this, arguments);
+    return possibleConstructorReturn(this, e);
+  };
+}
+export { _createSuper as default };