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/@babel/plugin-transform-numeric-separator/lib/index.js

@@ -0,0 +1,31 @@
+"use strict";
+
+Object.defineProperty(exports, "__esModule", {
+  value: true
+});
+exports.default = void 0;
+var _helperPluginUtils = require("@babel/helper-plugin-utils");
+function remover({
+  node
+}) {
+  var _extra$raw;
+  const {
+    extra
+  } = node;
+  if (extra != null && (_extra$raw = extra.raw) != null && _extra$raw.includes("_")) {
+    extra.raw = extra.raw.replace(/_/g, "");
+  }
+}
+var _default = exports.default = (0, _helperPluginUtils.declare)(api => {
+  api.assertVersion("^7.0.0-0 || ^8.0.0-0 || >8.0.0-alpha <8.0.0-beta");
+  return {
+    name: "transform-numeric-separator",
+    manipulateOptions: (_, parser) => parser.plugins.push("numericSeparator"),
+    visitor: {
+      NumericLiteral: remover,
+      BigIntLiteral: remover
+    }
+  };
+});
+
+//# sourceMappingURL=index.js.map