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/security-normalization.test.js

@@ -0,0 +1,39 @@
+'use strict'
+
+const test = require('tape')
+const fastURI = require('..')
+
+test('parse preserves reserved path escapes as data', (t) => {
+  const components = fastURI.parse('http://example.com/a%2Fb/public/%2e%2e/admin')
+
+  t.equal(components.path, '/a%2Fb/public/%2E%2E/admin')
+  t.end()
+})
+
+test('normalize preserves percent-encoded path separators and dot segments', (t) => {
+  t.equal(
+    fastURI.normalize('http://example.com/public/%2e%2e/admin'),
+    'http://example.com/public/%2E%2E/admin'
+  )
+
+  t.equal(
+    fastURI.normalize('http://example.com/a%2Fb'),
+    'http://example.com/a%2Fb'
+  )
+
+  t.end()
+})
+
+test('equal does not treat reserved path escapes as live path syntax', (t) => {
+  t.equal(
+    fastURI.equal('http://example.com/public/%2e%2e/admin', 'http://example.com/admin', {}),
+    false
+  )
+
+  t.equal(
+    fastURI.equal('http://example.com/a%2Fb', 'http://example.com/a/b', {}),
+    false
+  )
+
+  t.end()
+})