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/cast.mjs

@@ -0,0 +1,19 @@
+/**
+ * @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: "M2 8V6a2 2 0 0 1 2-2h16a2 2 0 0 1 2 2v12a2 2 0 0 1-2 2h-6", key: "3zrzxg" }],
+  ["path", { d: "M2 12a9 9 0 0 1 8 8", key: "g6cvee" }],
+  ["path", { d: "M2 16a5 5 0 0 1 4 4", key: "1y1dii" }],
+  ["line", { x1: "2", x2: "2.01", y1: "20", y2: "20", key: "xu2jvo" }]
+];
+const Cast = createLucideIcon("cast", __iconNode);
+
+export { __iconNode, Cast as default };
+//# sourceMappingURL=cast.mjs.map