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/preset-env/lib/polyfills/regenerator.cjs

@@ -0,0 +1,43 @@
+const {
+  getImportSource,
+  getRequireSource
+} = require("./utils.cjs");
+function isRegeneratorSource(source) {
+  return source === "regenerator-runtime/runtime" || source === "regenerator-runtime/runtime.js";
+}
+module.exports = function () {
+  const visitor = {
+    ImportDeclaration(path) {
+      if (isRegeneratorSource(getImportSource(path))) {
+        this.regeneratorImportExcluded = true;
+        path.remove();
+      }
+    },
+    Program(path) {
+      path.get("body").forEach(bodyPath => {
+        if (isRegeneratorSource(getRequireSource(bodyPath))) {
+          this.regeneratorImportExcluded = true;
+          bodyPath.remove();
+        }
+      });
+    }
+  };
+  return {
+    name: "preset-env/remove-regenerator",
+    visitor,
+    pre() {
+      this.regeneratorImportExcluded = false;
+    },
+    post() {
+      if (this.opts.debug && this.regeneratorImportExcluded) {
+        let filename = this.file.opts.filename;
+        if (process.env.BABEL_ENV === "test") {
+          filename = filename.replace(/\\/g, "/");
+        }
+        console.log(`\n[${filename}] Based on your targets, regenerator-runtime import excluded.`);
+      }
+    }
+  };
+};
+
+//# sourceMappingURL=regenerator.cjs.map