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-define-polyfill-provider/lib/meta-resolver.js

@@ -0,0 +1,51 @@
+"use strict";
+
+exports.__esModule = true;
+exports.default = createMetaResolver;
+var _utils = require("./utils");
+function createMetaResolver(polyfills) {
+  const {
+    static: staticP,
+    instance: instanceP,
+    global: globalP
+  } = polyfills;
+  return meta => {
+    if (meta.kind === "global" && globalP && (0, _utils.has)(globalP, meta.name)) {
+      return {
+        kind: "global",
+        desc: globalP[meta.name],
+        name: meta.name
+      };
+    }
+    if (meta.kind === "property" || meta.kind === "in") {
+      const {
+        placement,
+        object,
+        key
+      } = meta;
+      if (object && placement === "static") {
+        if (globalP && _utils.PossibleGlobalObjects.has(object) && (0, _utils.has)(globalP, key)) {
+          return {
+            kind: "global",
+            desc: globalP[key],
+            name: key
+          };
+        }
+        if (staticP && (0, _utils.has)(staticP, object) && (0, _utils.has)(staticP[object], key)) {
+          return {
+            kind: "static",
+            desc: staticP[object][key],
+            name: `${object}$${key}`
+          };
+        }
+      }
+      if (instanceP && (0, _utils.has)(instanceP, key)) {
+        return {
+          kind: "instance",
+          desc: instanceP[key],
+          name: `${key}`
+        };
+      }
+    }
+  };
+}