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-unicode-property-regex/lib/index.js

@@ -0,0 +1,26 @@
+"use strict";
+
+Object.defineProperty(exports, "__esModule", {
+  value: true
+});
+exports.default = void 0;
+var _helperCreateRegexpFeaturesPlugin = require("@babel/helper-create-regexp-features-plugin");
+var _helperPluginUtils = require("@babel/helper-plugin-utils");
+var _default = exports.default = (0, _helperPluginUtils.declare)((api, options) => {
+  api.assertVersion("^7.0.0-0 || ^8.0.0-0 || >8.0.0-alpha <8.0.0-beta");
+  const {
+    useUnicodeFlag = true
+  } = options;
+  if (typeof useUnicodeFlag !== "boolean") {
+    throw new Error(".useUnicodeFlag must be a boolean, or undefined");
+  }
+  return (0, _helperCreateRegexpFeaturesPlugin.createRegExpFeaturePlugin)({
+    name: "transform-unicode-property-regex",
+    feature: "unicodePropertyEscape",
+    options: {
+      useUnicodeFlag
+    }
+  });
+});
+
+//# sourceMappingURL=index.js.map