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/helper-validator-option/lib/index.js

@@ -0,0 +1,21 @@
+"use strict";
+
+Object.defineProperty(exports, "__esModule", {
+  value: true
+});
+Object.defineProperty(exports, "OptionValidator", {
+  enumerable: true,
+  get: function () {
+    return _validator.OptionValidator;
+  }
+});
+Object.defineProperty(exports, "findSuggestion", {
+  enumerable: true,
+  get: function () {
+    return _findSuggestion.findSuggestion;
+  }
+});
+var _validator = require("./validator.js");
+var _findSuggestion = require("./find-suggestion.js");
+
+//# sourceMappingURL=index.js.map