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/picomatch/index.js

@@ -0,0 +1,17 @@
+'use strict';
+
+const pico = require('./lib/picomatch');
+const utils = require('./lib/utils');
+
+function picomatch(glob, options, returnState = false) {
+  // default to os.platform()
+  if (options && (options.windows === null || options.windows === undefined)) {
+    // don't mutate the original options object
+    options = { ...options, windows: utils.isWindows() };
+  }
+
+  return pico(glob, options, returnState);
+}
+
+Object.assign(picomatch, pico);
+module.exports = picomatch;