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/es-abstract-get/test/GetMethod.js

@@ -0,0 +1,42 @@
+'use strict';
+
+var test = require('tape');
+var forEach = require('for-each');
+var v = require('es-value-fixtures');
+var debug = require('object-inspect');
+
+var GetMethod = require('../GetMethod');
+
+test('GetMethod', function (t) {
+	forEach(v.nonPropertyKeys, function (nonPropertyKey) {
+		t['throws'](
+			// @ts-expect-error
+			function () { return GetMethod({}, nonPropertyKey); },
+			TypeError,
+			debug(nonPropertyKey) + ' is not a Property Key'
+		);
+	});
+
+	t['throws'](
+		// @ts-expect-error
+		function () { return GetMethod({ 7: 7 }, 7); },
+		TypeError,
+		'Throws a TypeError if `P` is not a property key'
+	);
+
+	t.equal(GetMethod({}, 'a'), undefined, 'returns undefined if property is undefined');
+	t.equal(GetMethod({ a: null }, 'a'), undefined, 'returns undefined if property is null');
+	t.equal(GetMethod({ a: undefined }, 'a'), undefined, 'returns undefined if property is undefined');
+
+	var obj = { a: function () {} };
+	t['throws'](
+		// @ts-expect-error
+		function () { GetMethod({ a: 'b' }, 'a'); },
+		TypeError,
+		'throws a TypeError if property exists and is not callable'
+	);
+
+	t.equal(GetMethod(obj, 'a'), obj.a, 'returns property if it is callable');
+
+	t.end();
+});