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/2023/FindViaPredicate.js

@@ -0,0 +1,43 @@
+'use strict';
+
+var $TypeError = require('es-errors/type');
+var isInteger = require('math-intrinsics/isInteger');
+var isObject = require('es-object-atoms/isObject');
+
+var Call = require('./Call');
+var Get = require('./Get');
+var ToBoolean = require('./ToBoolean');
+var IsCallable = require('./IsCallable');
+var ToString = require('./ToString');
+
+// https://262.ecma-international.org/14.0/#sec-findviapredicate
+
+module.exports = function FindViaPredicate(O, len, direction, predicate, thisArg) {
+	if (!isObject(O)) {
+		throw new $TypeError('Assertion failed: Type(O) is not Object');
+	}
+	if (!isInteger(len) || len < 0) {
+		throw new $TypeError('Assertion failed: len must be a non-negative integer');
+	}
+	if (direction !== 'ascending' && direction !== 'descending') {
+		throw new $TypeError('Assertion failed: direction must be "ascending" or "descending"');
+	}
+
+	if (!IsCallable(predicate)) {
+		throw new $TypeError('predicate must be callable'); // step 1
+	}
+
+	for ( // steps 2-4
+		var k = direction === 'ascending' ? 0 : len - 1;
+		direction === 'ascending' ? k < len : k >= 0;
+		k += 1
+	) {
+		var Pk = ToString(k); // step 4.a
+		var kValue = Get(O, Pk); // step 4.c
+		var testResult = Call(predicate, thisArg, [kValue, k, O]); // step 4.d
+		if (ToBoolean(testResult)) {
+			return { '[[Index]]': k, '[[Value]]': kValue }; // step 4.e
+		}
+	}
+	return { '[[Index]]': -1, '[[Value]]': void undefined }; // step 5
+};