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-uri/test/util.test.js

@@ -0,0 +1,38 @@
+'use strict'
+
+const test = require('tape')
+const {
+  stringArrayToHexStripped,
+  removeDotSegments
+} = require('../lib/utils')
+
+test('stringArrayToHexStripped', (t) => {
+  const testCases = [
+    [['0', '0', '0', '0'], ''],
+    [['0', '0', '0', '1'], '1'],
+    [['0', '0', '1', '0'], '10'],
+    [['0', '1', '0', '0'], '100'],
+    [['1', '0', '0', '0'], '1000'],
+    [['1', '0', '0', '1'], '1001'],
+  ]
+
+  t.plan(testCases.length)
+
+  testCases.forEach(([input, expected]) => {
+    t.same(stringArrayToHexStripped(input), expected)
+  })
+})
+
+// Just fixtures, because this function already tested by resolve
+test('removeDotSegments', (t) => {
+  const testCases = []
+  // https://github.com/fastify/fast-uri/issues/139
+  testCases.push(['WS:/WS://1305G130505:1&%0D:1&C(XXXXX*)))))))XXX130505:UUVUaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa$aaaaaaaaaaaa13a',
+    'WS:/WS://1305G130505:1&%0D:1&C(XXXXX*)))))))XXX130505:UUVUaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa$aaaaaaaaaaaa13a'])
+
+  t.plan(testCases.length)
+
+  testCases.forEach(([input, expected]) => {
+    t.same(removeDotSegments(input), expected)
+  })
+})