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-modules-commonjs/lib/dynamic-import.js

@@ -0,0 +1,16 @@
+"use strict";
+
+Object.defineProperty(exports, "__esModule", {
+  value: true
+});
+exports.transformDynamicImport = transformDynamicImport;
+var _core = require("@babel/core");
+var _helperModuleTransforms = require("@babel/helper-module-transforms");
+const requireNoInterop = source => _core.template.expression.ast`require(${source})`;
+const requireInterop = (source, file) => _core.types.callExpression(file.addHelper("interopRequireWildcard"), [requireNoInterop(source)]);
+function transformDynamicImport(path, noInterop, file) {
+  const buildRequire = noInterop ? requireNoInterop : requireInterop;
+  path.replaceWith((0, _helperModuleTransforms.buildDynamicImport)(path.node, true, false, specifier => buildRequire(specifier, file)));
+}
+
+//# sourceMappingURL=dynamic-import.js.map