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/index.js

@@ -0,0 +1,37 @@
+'use strict';
+
+var callBound = require('call-bound');
+
+var toStr = callBound('Object.prototype.toString');
+
+var isIE68 = !(0 in [,]); // eslint-disable-line no-sparse-arrays, no-magic-numbers
+
+var objectClass = '[object Object]';
+var ddaClass = '[object HTMLAllCollection]';
+
+/** @type {(() => false) | ((value: unknown) => value is HTMLAllCollection)} */
+var isDDA = function isDocumentDotAll() {
+	return /** @type {const} */ (false);
+};
+if (typeof document === 'object') {
+	// Firefox 3 canonicalizes DDA to undefined when it's not accessed directly
+	var all = document.all;
+	if (toStr(all) === toStr(document.all)) {
+		isDDA = /** @type {import('.')} */ (function isDocumentDotAll(value) {
+			/* globals document: false */
+			// in IE 6-8, typeof document.all is "object" and it's truthy
+			if ((isIE68 || !value) && (typeof value === 'undefined' || typeof value === 'object')) {
+				try {
+					// @ts-expect-error nullish will throw
+					var str = toStr(value);
+					// IE 6-8 uses `objectClass`
+					return (str === ddaClass || str === objectClass)
+						&& /** @type {Function} */ (value)('') == null; // eslint-disable-line eqeqeq
+				} catch (e) { /**/ }
+			}
+			return false;
+		});
+	}
+}
+
+module.exports = isDDA;