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/jake/lib/utils/logger.js

@@ -0,0 +1,24 @@
+let util = require('util');
+
+let logger = new (function () {
+  let _output = function (type, out) {
+    let quiet = typeof jake != 'undefined' && jake.program &&
+        jake.program.opts && jake.program.opts.quiet;
+    let msg;
+    if (!quiet) {
+      msg = typeof out == 'string' ? out : util.inspect(out);
+      console[type](msg);
+    }
+  };
+
+  this.log = function (out) {
+    _output('log', out);
+  };
+
+  this.error = function (out) {
+    _output('error', out);
+  };
+
+})();
+
+module.exports = logger;