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/nanoid/non-secure/index.js

@@ -0,0 +1,24 @@
+let urlAlphabet =
+  'useandom-26T198340PX75pxJACKVERYMINDBUSHWOLF_GQZbfghjklqvwyzrict'
+
+let customAlphabet = (alphabet, defaultSize = 21) => {
+  return (size = defaultSize) => {
+    let id = ''
+    let i = size | 0
+    while (i--) {
+      id += alphabet[(Math.random() * alphabet.length) | 0]
+    }
+    return id
+  }
+}
+
+let nanoid = (size = 21) => {
+  let id = ''
+  let i = size | 0
+  while (i--) {
+    id += urlAlphabet[(Math.random() * 64) | 0]
+  }
+  return id
+}
+
+export { nanoid, customAlphabet }