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/is-document.all/test/index.js

@@ -0,0 +1,52 @@
+'use strict';
+
+var test = require('tape');
+var inspect = require('object-inspect');
+var forEach = require('for-each');
+var v = require('es-value-fixtures');
+
+var isDocumentAll = require('../');
+
+test('non-DDA values', function (t) {
+	/** @type {unknown[]} */
+	var nonDDAs = [].concat(
+		// @ts-expect-error TS sucks with concat
+		v.primitives,
+		v.objects,
+		[
+			[],
+			/a/g,
+			new Date(),
+			function () {}
+		]
+	);
+	forEach(nonDDAs, function (nonDDA) {
+		t.equal(isDocumentAll(nonDDA), false, inspect(nonDDA) + ' is not document.all');
+	});
+
+	t.end();
+});
+
+test('document.all', { skip: typeof document !== 'object' }, function (t) {
+	t.plan(4);
+
+	/* globals document: false */
+	t.equal(isDocumentAll(document.all), true, 'document.all is document.all');
+	t.equal(isDocumentAll(document), false, 'document is not document.all');
+
+	var iframe = document.createElement('iframe');
+	iframe.style.display = 'none'; // Optional: keep it hidden
+	document.body.appendChild(iframe);
+	t.teardown(function () { document.body.removeChild(iframe); });
+
+	iframe.onload = function () {
+		var doc = iframe.contentWindow && iframe.contentWindow.document;
+		t.equal(
+			isDocumentAll(doc && doc.all),
+			true,
+			'another realm’s document.all is document.all'
+		);
+		t.equal(isDocumentAll(doc), false, 'another realm’s document is not document.all');
+	};
+	iframe.src = 'about:blank'; // or point to a URL
+});