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/index.browser.cjs

@@ -0,0 +1,44 @@
+
+let { urlAlphabet } = require('./url-alphabet/index.cjs')
+
+let random = bytes => crypto.getRandomValues(new Uint8Array(bytes))
+
+let customRandom = (alphabet, defaultSize, getRandom) => {
+  let mask = (2 << (Math.log(alphabet.length - 1) / Math.LN2)) - 1
+
+
+
+  let step = -~((1.6 * mask * defaultSize) / alphabet.length)
+
+  return (size = defaultSize) => {
+    let id = ''
+    while (true) {
+      let bytes = getRandom(step)
+      let j = step | 0
+      while (j--) {
+        id += alphabet[bytes[j] & mask] || ''
+        if (id.length === size) return id
+      }
+    }
+  }
+}
+
+let customAlphabet = (alphabet, size = 21) =>
+  customRandom(alphabet, size, random)
+
+let nanoid = (size = 21) =>
+  crypto.getRandomValues(new Uint8Array(size)).reduce((id, byte) => {
+    byte &= 63
+    if (byte < 36) {
+      id += byte.toString(36)
+    } else if (byte < 62) {
+      id += (byte - 26).toString(36).toUpperCase()
+    } else if (byte > 62) {
+      id += '-'
+    } else {
+      id += '_'
+    }
+    return id
+  }, '')
+
+module.exports = { nanoid, customAlphabet, customRandom, urlAlphabet, random }