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/asyncGeneratorDelegate.js

@@ -0,0 +1,24 @@
+import OverloadYield from "./OverloadYield.js";
+function _asyncGeneratorDelegate(t) {
+  var e = {},
+    n = !1;
+  function pump(e, r) {
+    return n = !0, r = new Promise(function (n) {
+      n(t[e](r));
+    }), {
+      done: !1,
+      value: new OverloadYield(r, 1)
+    };
+  }
+  return e["undefined" != typeof Symbol && Symbol.iterator || "@@iterator"] = function () {
+    return this;
+  }, e.next = function (t) {
+    return n ? (n = !1, t) : pump("next", t);
+  }, "function" == typeof t["throw"] && (e["throw"] = function (t) {
+    if (n) throw n = !1, t;
+    return pump("throw", t);
+  }), "function" == typeof t["return"] && (e["return"] = function (t) {
+    return n ? (n = !1, t) : pump("return", t);
+  }), e;
+}
+export { _asyncGeneratorDelegate as default };