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/which-boxed-primitive/test/index.js

@@ -0,0 +1,46 @@
+'use strict';
+
+var test = require('tape');
+var inspect = require('object-inspect');
+var forEach = require('for-each');
+var v = require('es-value-fixtures');
+
+var whichBoxedPrimitive = require('../');
+
+var objects = [
+	/a/g,
+	new Date(),
+	function () {},
+	[],
+	{}
+].concat(v.objects);
+
+test('isBoxedPrimitive', function (t) {
+	t.test('unboxed primitives', function (st) {
+		forEach(v.primitives, function (primitive) {
+			st.equal(null, whichBoxedPrimitive(primitive), inspect(primitive) + ' is a primitive, but not a boxed primitive');
+		});
+		st.end();
+	});
+
+	t.test('boxed primitives', function (st) {
+		forEach(v.primitives, function (primitive) {
+			if (primitive != null) { // eslint-disable-line eqeqeq
+				var boxed = Object(primitive);
+				var expected = boxed.constructor.name;
+				st.equal(typeof expected, 'string', 'expected is string');
+				st.equal(whichBoxedPrimitive(boxed), expected, inspect(boxed) + ' is a boxed primitive: ' + expected);
+			}
+		});
+		st.end();
+	});
+
+	t.test('non-primitive objects', function (st) {
+		forEach(objects, function (object) {
+			st.equal(undefined, whichBoxedPrimitive(object), inspect(object) + ' is not a primitive, boxed or otherwise');
+		});
+		st.end();
+	});
+
+	t.end();
+});