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/fast-json-stable-stringify/benchmark/index.js

@@ -0,0 +1,31 @@
+'use strict';
+
+const Benchmark = require('benchmark');
+const suite = new Benchmark.Suite;
+const testData = require('./test.json');
+
+
+const stringifyPackages = {
+  // 'JSON.stringify': JSON.stringify,
+  'fast-json-stable-stringify': require('../index'),
+  'json-stable-stringify': true,
+  'fast-stable-stringify': true,
+  'faster-stable-stringify': true
+};
+
+
+for (const name in stringifyPackages) {
+  let func = stringifyPackages[name];
+  if (func === true) func = require(name);
+
+  suite.add(name, function() {
+    func(testData);
+  });
+}
+
+suite
+  .on('cycle', (event) => console.log(String(event.target)))
+  .on('complete', function () {
+    console.log('The fastest is ' + this.filter('fastest').map('name'));
+  })
+  .run({async: true});

frontend/node_modules/fast-json-stable-stringify/benchmark/test.json

@@ -0,0 +1,137 @@
+[
+  {
+    "_id": "59ef4a83ee8364808d761beb",
+    "index": 0,
+    "guid": "e50ffae9-7128-4148-9ee5-40c3fc523c5d",
+    "isActive": false,
+    "balance": "$2,341.81",
+    "picture": "http://placehold.it/32x32",
+    "age": 28,
+    "eyeColor": "brown",
+    "name": "Carey Savage",
+    "gender": "female",
+    "company": "VERAQ",
+    "email": "careysavage@veraq.com",
+    "phone": "+1 (897) 574-3014",
+    "address": "458 Willow Street, Henrietta, California, 7234",
+    "about": "Nisi reprehenderit nulla ad officia pariatur non dolore laboris irure cupidatat laborum. Minim eu ex Lorem adipisicing exercitation irure minim sunt est enim mollit incididunt voluptate nulla. Ut mollit anim reprehenderit et aliqua ex esse aliquip. Aute sit duis deserunt do incididunt consequat minim qui dolor commodo deserunt et voluptate.\r\n",
+    "registered": "2014-05-21T01:56:51 -01:00",
+    "latitude": 63.89502,
+    "longitude": 62.369807,
+    "tags": [
+      "nostrud",
+      "nisi",
+      "consectetur",
+      "ullamco",
+      "cupidatat",
+      "culpa",
+      "commodo"
+    ],
+    "friends": [
+      {
+        "id": 0,
+        "name": "Henry Walls"
+      },
+      {
+        "id": 1,
+        "name": "Janice Baker"
+      },
+      {
+        "id": 2,
+        "name": "Russell Bush"
+      }
+    ],
+    "greeting": "Hello, Carey Savage! You have 4 unread messages.",
+    "favoriteFruit": "banana"
+  },
+  {
+    "_id": "59ef4a83ff5774a691454e89",
+    "index": 1,
+    "guid": "2bee9efc-4095-4c2e-87ef-d08c8054c89d",
+    "isActive": true,
+    "balance": "$1,618.15",
+    "picture": "http://placehold.it/32x32",
+    "age": 35,
+    "eyeColor": "blue",
+    "name": "Elinor Pearson",
+    "gender": "female",
+    "company": "FLEXIGEN",
+    "email": "elinorpearson@flexigen.com",
+    "phone": "+1 (923) 548-3751",
+    "address": "600 Bayview Avenue, Draper, Montana, 3088",
+    "about": "Mollit commodo ea sit Lorem velit. Irure anim esse Lorem sint quis officia ut. Aliqua nisi dolore in aute deserunt mollit ex ea in mollit.\r\n",
+    "registered": "2017-04-22T07:58:41 -01:00",
+    "latitude": -87.824919,
+    "longitude": 69.538927,
+    "tags": [
+      "fugiat",
+      "labore",
+      "proident",
+      "quis",
+      "eiusmod",
+      "qui",
+      "est"
+    ],
+    "friends": [
+      {
+        "id": 0,
+        "name": "Massey Wagner"
+      },
+      {
+        "id": 1,
+        "name": "Marcella Ferrell"
+      },
+      {
+        "id": 2,
+        "name": "Evans Mckee"
+      }
+    ],
+    "greeting": "Hello, Elinor Pearson! You have 3 unread messages.",
+    "favoriteFruit": "strawberry"
+  },
+  {
+    "_id": "59ef4a839ec8a4be4430b36b",
+    "index": 2,
+    "guid": "ddd6e8c0-95bd-416d-8b46-a768d6363809",
+    "isActive": false,
+    "balance": "$2,046.95",
+    "picture": "http://placehold.it/32x32",
+    "age": 40,
+    "eyeColor": "green",
+    "name": "Irwin Davidson",
+    "gender": "male",
+    "company": "DANJA",
+    "email": "irwindavidson@danja.com",
+    "phone": "+1 (883) 537-2041",
+    "address": "439 Cook Street, Chapin, Kentucky, 7398",
+    "about": "Irure velit non commodo aliqua exercitation ut nostrud minim magna. Dolor ad ad ut irure eu. Non pariatur dolor eiusmod ipsum do et exercitation cillum. Et amet laboris minim eiusmod ullamco magna ea reprehenderit proident sunt.\r\n",
+    "registered": "2016-09-01T07:49:08 -01:00",
+    "latitude": -49.803812,
+    "longitude": 104.93279,
+    "tags": [
+      "consequat",
+      "enim",
+      "quis",
+      "magna",
+      "est",
+      "culpa",
+      "tempor"
+    ],
+    "friends": [
+      {
+        "id": 0,
+        "name": "Ruth Hansen"
+      },
+      {
+        "id": 1,
+        "name": "Kathrine Austin"
+      },
+      {
+        "id": 2,
+        "name": "Rivera Munoz"
+      }
+    ],
+    "greeting": "Hello, Irwin Davidson! You have 2 unread messages.",
+    "favoriteFruit": "banana"
+  }
+]