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/regeneratorAsyncIterator.js

@@ -0,0 +1,33 @@
+var OverloadYield = require("./OverloadYield.js");
+var regeneratorDefine = require("./regeneratorDefine.js");
+function AsyncIterator(t, e) {
+  function n(r, o, i, f) {
+    try {
+      var c = t[r](o),
+        u = c.value;
+      return u instanceof OverloadYield ? e.resolve(u.v).then(function (t) {
+        n("next", t, i, f);
+      }, function (t) {
+        n("throw", t, i, f);
+      }) : e.resolve(u).then(function (t) {
+        c.value = t, i(c);
+      }, function (t) {
+        return n("throw", t, i, f);
+      });
+    } catch (t) {
+      f(t);
+    }
+  }
+  var r;
+  this.next || (regeneratorDefine(AsyncIterator.prototype), regeneratorDefine(AsyncIterator.prototype, "function" == typeof Symbol && Symbol.asyncIterator || "@asyncIterator", function () {
+    return this;
+  })), regeneratorDefine(this, "_invoke", function (t, o, i) {
+    function f() {
+      return new e(function (e, r) {
+        n(t, i, e, r);
+      });
+    }
+    return r = r ? r.then(f, f) : f();
+  }, !0);
+}
+module.exports = AsyncIterator, module.exports.__esModule = true, module.exports["default"] = module.exports;