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/lucide-react/dist/esm/icons/message-square-x.mjs

@@ -0,0 +1,24 @@
+/**
+ * @license lucide-react v1.24.0 - ISC
+ *
+ * This source code is licensed under the ISC license.
+ * See the LICENSE file in the root directory of this source tree.
+ */
+
+import createLucideIcon from '../createLucideIcon.mjs';
+
+const __iconNode = [
+  [
+    "path",
+    {
+      d: "M22 17a2 2 0 0 1-2 2H6.828a2 2 0 0 0-1.414.586l-2.202 2.202A.71.71 0 0 1 2 21.286V5a2 2 0 0 1 2-2h16a2 2 0 0 1 2 2z",
+      key: "18887p"
+    }
+  ],
+  ["path", { d: "m14.5 8.5-5 5", key: "19tnj2" }],
+  ["path", { d: "m9.5 8.5 5 5", key: "1oa8ql" }]
+];
+const MessageSquareX = createLucideIcon("message-square-x", __iconNode);
+
+export { __iconNode, MessageSquareX as default };
+//# sourceMappingURL=message-square-x.mjs.map